# 2014 United States Senate election in Colorado

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The 2014 United States Senate election in Colorado was held on November 4, 2014, to elect a member of the United States Senate to represent the State of Colorado, concurrently with the election of the Governor of Colorado, other elections to the United States Senate, elections to the United States House of Representatives, and various state and local elections. Incumbent Democratic Senator Mark Udall ran for re-election to a second term, but narrowly lost to Republican U.S. Representative Cory Gardner by a margin of 1.9 percent.
Despite Gardner's win however, with slightly over 48% of the vote, it is the lowest a winning Republican had received in the Class 2 Senate seat since 1918.
As of 2025, this is the last time that a Republican has won a Senate election in the state.

## Democratic primary

Mark Udall was the only Democrat to file to run, and thus at the Democratic state assembly on April 12, 2014, he was renominated unopposed.

### Candidates
#### Nominee

* Mark Udall, incumbent U.S. Senator

### Results

Democratic primary results :
| Party | Party | Candidate | Votes | % |
| | Democratic | Mark Udall (incumbent) | 213,746 | 100.00% |
| Total votes | Total votes | Total votes | 213,746 | 100.00% |

## Republican primary

At the Republican state assembly on April 12, 2014, Cory Gardner received 73% of the votes of over 3,900 delegates. Neither Randy Baumgardner nor Tom Janich received the required 30% make the ballot and thus Gardner received the party's nomination.

### Candidates
#### Nominee

* Cory Gardner, U.S. Representative

#### Rejected in convention

* Randy Baumgardner, state senator
* Tom Janich, perennial candidate

#### Withdrew

* Mark Aspiri, businessman
* Ken Buck, Weld County District Attorney and nominee for the U.S. Senate in 2010 (running for CO-04)
* Owen Hill, state senator
* Jaime McMillan, businessman
* Amy Stephens, state representative
* Floyd Trujillo, businessman

#### Declined

* Bob Beauprez, former U.S. Representative and nominee for Governor in 2006 (running for Governor)
* Mike Coffman, U.S. Representative
* Dan Domenico, Solicitor General of Colorado
* Doug Lamborn, U.S. Representative
* Jane E. Norton, former lieutenant governor of Colorado and candidate for the U.S. Senate in 2010
* Scott Renfroe, state senator
* Victor E. Renuart Jr., former commander of United States Northern Command and the North American Aerospace Defense Command
* Ellen Roberts, state senator
* John Suthers, Attorney General of Colorado
* Scott Tipton, U.S. Representative

### Endorsements

Individuals
* Ken Buck, Weld County District Attorney and former candidate for U.S. Senate
* Rick Santorum, former U.S. Senator from Pennsylvania and candidate for President of the United States in 2012
* Amy Stephens, State Representative and former candidate for U.S. Senate
Newspapers
* The Denver Post

### Polling

| Poll source | Date(s) administered | Sample size | Margin of error | Mark Aspiri | Randy Baumgardner | Cory Gardner | Owen Hill | Tom Janich | Floyd Trujillo | Other | Undecided |
| Public Policy Polling | March 13–16, 2014 | 255 | ± 6.1% | 3% | 15% | 44% | 6% | 4% | 0% | — | 29% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Aspiri | Randy Baumgardner | Ken Buck | Owen Hill | Jaime McMillan | Amy Stephens | Other | Undecided |
| Public Policy Polling | December 3–4, 2013 | 335 | ± 5.2% | 0% | 8% | 45% | 2% | 1% | 7% | — | 37% |

### Results

Republican primary results :
| Party | Party | Candidate | Votes | % |
| | Republican | Cory Gardner | 338,324 | 100.00% |
| Total votes | Total votes | Total votes | 338,324 | 100.00% |

## Libertarian Party
### Candidates
#### Nominated

* Gaylon Kent, candidate for Colorado's 3rd congressional district in 2012

## Unity Party of America
### Candidates
#### Nominated

* Bill Hammons, founder and National Chairman of the Unity Party of America

## Independents
### Candidates
#### Declared

* Raúl Acosta, IT professional
* Steve Shogan, neurosurgeon

## General election
### Fundraising

| Candidate | Raised | Spent | Cash on Hand |
| Mark Udall (D) | $14,088,510 | $15,746,249 | $536,332 |
| Cory Gardner (R) | $9,680,263 | $9,100,730 | $1,875,029 |

### Debates

* Complete video of debate, October 6, 2014
* Complete video of debate, October 15, 2014

### Predictions

| Source | Ranking | As of |
| The Cook Political Report | Tossup | November 3, 2014 |
| Sabato's Crystal Ball | Lean R (flip) | November 3, 2014 |
| Rothenberg Political Report | Tilt R (flip) | November 3, 2014 |
| Real Clear Politics | Tossup | November 3, 2014 |

### Polling

| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Cory Gardner (R) | Other | Undecided |
| Public Policy Polling | November 1–2, 2014 | 739 | ± 3.6% | 45% | 48% | 5% | 3% |
| Public Policy Polling | November 1–2, 2014 | 739 | ± 3.6% | 47% | 50% | — | 3% |
| Quinnipiac University | October 28 – November 2, 2014 | 815 | ± 3.4% | 43% | 45% | 7% | 4% |
| Quinnipiac University | October 28 – November 2, 2014 | 815 | ± 3.4% | 45% | 46% | 2% | 6% |
| YouGov | October 25–31, 2014 | 1,417 | ± 3.3% | 42% | 43% | 5% | 11% |
| Public Policy Polling | October 28–29, 2014 | 573 | ± ? | 48% | 48% | — | 4% |
| SurveyUSA | October 27–29, 2014 | 618 | ± 4% | 44% | 46% | 5% | 5% |
| Vox Populi Polling | October 26–27, 2014 | 642 | ± 3.9% | 43% | 46% | — | 10% |
| Quinnipiac University | October 22–27, 2014 | 844 | ± 3.4% | 39% | 46% | 8% | 7% |
| Quinnipiac University | October 22–27, 2014 | 844 | ± 3.4% | 41% | 49% | 2% | 9% |
| Strategies 360 | October 20–25, 2014 | 604 | ± 4% | 45% | 44% | 4% | 8% |
| Rasmussen Reports | October 21–23, 2014 | 966 | ± 3% | 45% | 51% | 2% | 2% |
| Harstad Strategic Research | October 19–23, 2014 | 1,004 | ± ? | 44% | 43% | 6% | 6% |
| CBS News/NYT/YouGov | October 16–23, 2014 | 1,611 | ± 4% | 47% | 46% | 1% | 6% |
| NBC News/Marist | October 18–22, 2014 | 755 LV | ± 3.6% | 45% | 46% | 3% | 5% |
| NBC News/Marist | October 18–22, 2014 | 953 RV | ± 3.2% | 45% | 44% | 3% | 8% |
| Suffolk University | October 18–21, 2014 | 500 | ± 4.4% | 39% | 46% | 6% | 9% |
| Quinnipiac University | October 15–21, 2014 | 974 | ± 3.1% | 41% | 46% | 6% | 6% |
| Quinnipiac University | October 15–21, 2014 | 974 | ± 3.1% | 44% | 48% | 2% | 7% |
| Monmouth University | October 17–20, 2014 | 431 | ± 4.7% | 46% | 47% | 4% | 3% |
| IPSOS | October 13–20, 2014 | 1,099 | ± 3.4% | 45% | 47% | — | 8% |
| Public Policy Polling | October 16–19, 2014 | 778 | ± 3.5% | 43% | 46% | 5% | 7% |
| Public Policy Polling | October 16–19, 2014 | 778 | ± 3.5% | 44% | 47% | — | 9% |
| Gravis Marketing | October 16, 2014 | 695 | ± 4% | 43% | 48% | 4% | 5% |
| Benenson Strategy Group | October 15–16, 2014 | 600 | ± ? | 47% | 44% | 1% | 8% |
| Mellman Group | October 13–15, 2014 | 800 | ± 3.5% | 44% | 41% | — | 15% |
| CNN/ORC | October 9–13, 2014 | 665 | ± 4% | 46% | 50% | — | 4% |
| Quinnipiac University | October 8–13, 2014 | 988 | ± 3.1% | 41% | 47% | 8% | 4% |
| Quinnipiac University | October 8–13, 2014 | 988 | ± 3.1% | 44% | 49% | 1% | 7% |
| SurveyUSA | October 9–12, 2014 | 591 | ± 4.1% | 43% | 45% | 6% | 7% |
| High Point University | October 4–8, 2014 | 800 | ± 3.5% | 42% | 46% | 7% | 5% |
| Fox News | October 4–7, 2014 | 739 | ± 3.5% | 37% | 43% | 7% | 12% |
| Greenberg Quinlan Rosner | September 25 – October 1, 2014 | 1,000 | ± 2.09% | 45% | 45% | 10% | 10% |
| CBS News/NYT/YouGov | September 20 – October 1, 2014 | 1,634 | ± 3% | 48% | 45% | 1% | 6% |
| Rasmussen Reports | September 29–30, 2014 | 950 | ± 3% | 47% | 48% | 2% | 3% |
| Public Policy Polling | September 19–21, 2014 | 652 | ± 3.8% | 45% | 47% | — | 8% |
| ccAdvertising | September 19–21, 2014 | 2,094 | ± ? | 32% | 38% | — | 30% |
| Gravis Marketing | September 16–17, 2014 | 657 | ± 4% | 39% | 46% | 6% | 9% |
| Suffolk University | September 9–16, 2014 | 500 | ± 4.4% | 42% | 43% | 6% | 10% |
| Quinnipiac | September 10–15, 2014 | 1,211 | ± 2.8% | 40% | 48% | 8% | 3% |
| Quinnipiac | September 10–15, 2014 | 1,211 | ± 2.8% | 42% | 52% | 1% | 5% |
| Myers | September 7–14, 2014 | 1,350 | ± 2.7% | 48% | 46% | 2% | 3% |
| SurveyUSA | September 8–10, 2014 | 664 | ± 3.9% | 46% | 42% | 5% | 7% |
| Rasmussen Reports | September 3–4, 2014 | 800 | ± 4% | 44% | 42% | 4% | 10% |
| NBC News/Marist | September 2–4, 2014 | 795 LV | ± 3.5% | 48% | 42% | 1% | 9% |
| NBC News/Marist | September 2–4, 2014 | 976 RV | ± 3.1% | 48% | 40% | 1% | 11% |
| CBS News/NYT/YouGov | August 18 – September 2, 2014 | 1,727 | ± 4% | 46% | 43% | 2% | 9% |
| CBS News/New York Times | July 5–24, 2014 | 2,020 | ± 3% | 50% | 46% | 2% | 2% |
| Public Policy Polling | July 17–20, 2014 | 653 | ± 3.8% | 44% | 43% | — | 13% |
| Quinnipiac | July 10–14, 2014 | 1,147 | ± 2.9% | 42% | 44% | 1% | 13% |
| Gravis Marketing | July 7–10, 2014 | 1,106 | ± 3% | 43% | 47% | 6% | 4% |
| NBC News/Marist | July 7–10, 2014 | 914 | ± 3.2% | 48% | 41% | 2% | 10% |
| Rasmussen Reports | June 25–26, 2014 | 750 | ± 4% | 43% | 42% | 6% | 9% |
| Magellan Strategies | June 6–8, 2014 | 747 | ± 3.54% | 45% | 47% | — | 8% |
| Public Policy Polling | May 7–8, 2014 | 526 | ± ? | 47% | 43% | — | 10% |
| Quinnipiac | April 15–21, 2014 | 1,298 | ± 2.7% | 45% | 44% | 1% | 9% |
| Public Policy Polling | April 17–20, 2014 | 618 | ± ? | 47% | 45% | — | 8% |
| Fabrizio, Lee & Associates | April 16–17, 2014 | 600 | ± 4% | 42% | 44% | 7% | 7% |
| Magellan Strategies | April 14–15, 2014 | 717 | ± 3.7% | 45% | 42% | 5% | 8% |
| Harper Polling | April 7–9, 2014 | 507 | ± 4.35% | 45% | 43% | — | 12% |
| Public Policy Polling | March 13–16, 2014 | 568 | ± 4.1% | 42% | 40% | — | 17% |
| Harper Polling | March 8–9, 2014 | 689 | ± ? | 45% | 44% | — | 17% |
| Rasmussen Reports | March 5–6, 2014 | 500 | ± 4.5% | 42% | 41% | 5% | 13% |
| Public Policy Polling | April 11–14, 2013 | 500 | ± 4.4% | 49% | 39% | — | 12% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Mark Aspiri (R) | Other | Undecided |
| Quinnipiac | November 15–18, 2013 | 1,206 | ± 2.8% | 45% | 36% | 1% | 17% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Randy Baumgardner (R) | Other | Undecided |
| Public Policy Polling | March 13–16, 2014 | 568 | ± 4.1% | 44% | 37% | — | 19% |
| Quinnipiac | January 29 – February 2, 2014 | 1,139 | ± 2.9% | 43% | 41% | 1% | 15% |
| Public Policy Polling | December 3–4, 2013 | 928 | ± 3.2% | 47% | 40% | — | 13% |
| Quinnipiac | November 15–18, 2013 | 1,206 | ± 2.8% | 44% | 39% | 1% | 16% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Bob Beauprez (R) | Other | Undecided |
| Public Policy Polling | April 11–14, 2013 | 500 | ± 4.4% | 48% | 41% | — | 11% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Ken Buck (R) | Other | Undecided |
| Hickman Analytics | February 17–20, 2014 | 400 | ± 4.9% | 46% | 42% | — | 12% |
| Quinnipiac | January 29 – February 2, 2014 | 1,139 | ± 2.9% | 45% | 42% | 1% | 13% |
| Public Policy Polling | December 3–4, 2013 | 928 | ± 3.2% | 46% | 42% | — | 12% |
| Quinnipiac | November 15–18, 2013 | 1,206 | ± 2.8% | 45% | 42% | 1% | 12% |
| Public Policy Polling | June 14–17, 2012 | 799 | ± 3.5% | 50% | 35% | — | 15% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Mike Coffman (R) | Other | Undecided |
| Public Policy Polling | June 14–17, 2012 | 799 | ± 3.5% | 48% | 39% | — | 13% |
| Public Policy Polling | December 1–4, 2011 | 793 | ± 3.5% | 48% | 34% | — | 18% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Scott Gessler (R) | Other | Undecided |
| Public Policy Polling | April 11–14, 2013 | 500 | ± 4.4% | 50% | 37% | — | 13% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Owen Hill (R) | Other | Undecided |
| Public Policy Polling | March 13–16, 2014 | 568 | ± 4.1% | 43% | 38% | — | 19% |
| Quinnipiac | January 29 – February 2, 2014 | 1,139 | ± 2.9% | 44% | 39% | 1% | 16% |
| Public Policy Polling | December 3–4, 2013 | 928 | ± 3.2% | 44% | 37% | — | 18% |
| Quinnipiac | November 15–18, 2013 | 1,206 | ± 2.8% | 45% | 39% | 1% | 16% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Doug Lamborn (R) | Other | Undecided |
| Public Policy Polling | June 14–17, 2012 | 799 | ± 3.5% | 49% | 36% | — | 15% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Jaime McMillan (R) | Other | Undecided |
| Quinnipiac | January 29 – February 2, 2014 | 1,139 | ± 2.9% | 45% | 38% | 1% | 16% |
| Quinnipiac | November 15–18, 2013 | 1,206 | ± 2.8% | 43% | 40% | 1% | 17% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Jane Norton (R) | Other | Undecided |
| Public Policy Polling | April 11–14, 2013 | 500 | ± 4.4% | 49% | 38% | — | 13% |
| Public Policy Polling | June 14–17, 2012 | 799 | ± 3.5% | 48% | 38% | — | 14% |
| Public Policy Polling | December 1–4, 2011 | 793 | ± 3.5% | 50% | 33% | — | 17% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Bill Owens (R) | Other | Undecided |
| Public Policy Polling | June 14–17, 2012 | 799 | ± 3.5% | 47% | 43% | — | 10% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Walker Stapleton (R) | Other | Undecided |
| Public Policy Polling | April 11–14, 2013 | 500 | ± 4.4% | 50% | 37% | — | 13% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Amy Stephens (R) | Other | Undecided |
| Quinnipiac | January 29 – February 2, 2014 | 1,139 | ± 2.9% | 43% | 41% | 1% | 15% |
| Public Policy Polling | December 3–4, 2013 | 928 | ± 3.2% | 44% | 37% | — | 19% |
| Quinnipiac | November 15–18, 2013 | 1,206 | ± 2.8% | 45% | 38% | 1% | 16% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | John Suthers (R) | Other | Undecided |
| Public Policy Polling | April 11–14, 2013 | 500 | ± 4.4% | 50% | 38% | — | 12% |
| Public Policy Polling | June 14–17, 2012 | 799 | ± 3.5% | 48% | 38% | — | 14% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Tom Tancredo (R) | Other | Undecided |
| Public Policy Polling | April 11–14, 2013 | 500 | ± 4.4% | 51% | 39% | — | 11% |
| Public Policy Polling | June 14–17, 2012 | 799 | ± 3.5% | 49% | 39% | — | 11% |
| Poll source | Date(s) administered | Sample size | Margin of error | Mark Udall (D) | Scott Tipton (R) | Other | Undecided |
| Public Policy Polling | April 11–14, 2013 | 500 | ± 4.4% | 50% | 37% | — | 13% |

### Results

United States Senate election in Colorado, 2014 :
| Party | Party | Candidate | Votes | % | ±% |
| | Republican | Cory Gardner | 983,891 | 48.21% | +5.72% |
| | Democratic | Mark Udall (incumbent) | 944,203 | 46.26% | −6.54% |
| | Libertarian | Gaylon Kent | 52,876 | 2.59% | N/A |
| | Independent | Steve Shogan | 29,472 | 1.44% | N/A |
| | Independent | Raúl Acosta | 24,151 | 1.18% | N/A |
| | Unity | Bill Hammons | 6,427 | 0.32% | N/A |
| Total votes | Total votes | Total votes | 2,041,020 | 100.00% | N/A |
| | Republican gain from Democratic | Republican gain from Democratic | Republican gain from Democratic | Republican gain from Democratic | Republican gain from Democratic |

#### By county

| County | Udall% | Udall# | Gardner% | Gardner# | Others% | Others# | Total |
| Adams | 47.70% | 62,296 | 44.88% | 58,614 | 7.42% | 9,703 | 130,613 |
| Alamosa | 47.42% | 2,440 | 45.67% | 2,350 | 6.91% | 356 | 5,146 |
| Arapahoe | 48.02% | 107,347 | 46.48% | 103,915 | 5.50% | 12,284 | 223,546 |
| Archuleta | 37.23% | 2,030 | 56.90% | 3,103 | 5.87% | 320 | 5,453 |
| Baca | 18.99% | 353 | 73.91% | 1,374 | 7.10% | 132 | 1,859 |
| Bent | 32.14% | 503 | 60.64% | 949 | 7.22% | 113 | 1,565 |
| Boulder | 68.59% | 97,612 | 27.35% | 38,931 | 4.06% | 5,778 | 142,321 |
| Broomfield | 48.20% | 13,309 | 46.48% | 12,833 | 5.32% | 1,469 | 27,611 |
| Chaffee | 45.21% | 4,025 | 49.35% | 4,393 | 5.44% | 489 | 8,907 |
| Cheyenne | 11.75% | 122 | 81.70% | 848 | 6.55% | 68 | 1,038 |
| Clear Creek | 50.41% | 2,344 | 42.73% | 1,987 | 6.86% | 319 | 4,650 |
| Conejos | 46.78% | 1,621 | 47.88% | 1,659 | 5.34% | 185 | 3,465 |
| Costilla | 65.10% | 912 | 28.27% | 396 | 6.63% | 93 | 1,401 |
| Crowley | 25.67% | 344 | 65.52% | 878 | 8.81% | 118 | 1,340 |
| Custer | 29.41% | 740 | 65.94% | 1,659 | 4.65% | 117 | 2,516 |
| Delta | 26.07% | 3,504 | 68.44% | 9,199 | 5.49% | 737 | 13,440 |
| Denver | 70.73% | 163,783 | 24.53% | 56,789 | 4.74% | 10,981 | 231,553 |
| Dolores | 25.47% | 246 | 67.60% | 653 | 6.93% | 67 | 966 |
| Douglas | 32.77% | 45,163 | 62.86% | 86,626 | 4.37% | 6,020 | 137,809 |
| Eagle | 54.41% | 9,438 | 40.94% | 7,102 | 4.65% | 807 | 17,347 |
| El Paso | 32.09% | 73,208 | 62.01% | 141,475 | 5.90% | 13,471 | 228,154 |
| Elbert | 20.52% | 2,556 | 73.34% | 9,137 | 6.14% | 766 | 12,459 |
| Fremont | 27.72% | 4,773 | 64.37% | 11,085 | 7.91% | 1,363 | 17,221 |
| Garfield | 43.44% | 8,387 | 51.24% | 9,894 | 5.32% | 1,028 | 19,309 |
| Gilpin | 50.43% | 1,450 | 40.66% | 1,169 | 8.91% | 256 | 2,875 |
| Grand | 41.11% | 2,795 | 53.51% | 3,638 | 5.38% | 366 | 6,799 |
| Gunnison | 55.39% | 3,840 | 38.53% | 2,671 | 6.08% | 422 | 6,933 |
| Hinsdale | 36.52% | 191 | 58.70% | 307 | 4.78% | 25 | 523 |
| Huerfano | 47.04% | 1,504 | 45.32% | 1,449 | 7.64% | 244 | 3,197 |
| Jackson | 22.18% | 163 | 72.24% | 531 | 5.58% | 41 | 735 |
| Jefferson | 47.28% | 121,109 | 46.94% | 120,240 | 5.78% | 14,795 | 256,144 |
| Kiowa | 14.06% | 107 | 80.95% | 616 | 4.99% | 38 | 761 |
| Kit Carson | 15.71% | 487 | 78.97% | 2,448 | 5.32% | 165 | 3,100 |
| La Plata | 51.80% | 11,852 | 44.47% | 10,174 | 3.73% | 853 | 22,852 |
| Lake | 53.69% | 1,311 | 37.10% | 906 | 9.21% | 225 | 2,442 |
| Larimer | 47.13% | 68,659 | 47.50% | 69,198 | 5.37% | 7,815 | 145,672 |
| Las Animas | 42.77% | 2,380 | 50.38% | 2,803 | 6.85% | 381 | 5,564 |
| Lincoln | 16.07% | 321 | 77.93% | 1,557 | 6.00% | 120 | 1,998 |
| Logan | 20.61% | 1,591 | 73.34% | 5,662 | 6.05% | 467 | 7,720 |
| Mesa | 26.80% | 15,410 | 68.38% | 39,313 | 4.82% | 2,768 | 57,491 |
| Mineral | 42.26% | 254 | 50.58% | 304 | 7.16% | 43 | 601 |
| Moffat | 16.95% | 826 | 76.47% | 3,727 | 6.58% | 321 | 4,874 |
| Montezuma | 34.58% | 3,353 | 59.65% | 5,784 | 5.77% | 560 | 9,697 |
| Montrose | 24.45% | 4,071 | 71.52% | 11,907 | 4.03% | 671 | 16,649 |
| Morgan | 24.56% | 2,164 | 69.44% | 6,119 | 6.00% | 529 | 8,812 |
| Otero | 35.12% | 2,332 | 57.43% | 3,814 | 7.45% | 495 | 6,641 |
| Ouray | 50.39% | 1,355 | 45.89% | 1,234 | 3.72% | 100 | 2,689 |
| Park | 35.18% | 2,827 | 58.16% | 4,673 | 6.66% | 535 | 8,035 |
| Phillips | 18.06% | 357 | 76.68% | 1,516 | 5.26% | 104 | 1,977 |
| Pitkin | 69.80% | 5,409 | 27.18% | 2,106 | 3.02% | 234 | 7,749 |
| Prowers | 22.28% | 887 | 72.19% | 2,874 | 5.53% | 220 | 3,981 |
| Pueblo | 46.73% | 27,877 | 46.22% | 27,571 | 7.05% | 4,209 | 59,657 |
| Rio Blanco | 13.27% | 361 | 81.37% | 2,214 | 5.36% | 146 | 2,721 |
| Rio Grande | 35.25% | 1,566 | 57.05% | 2,534 | 7.70% | 342 | 4,442 |
| Routt | 53.95% | 5,639 | 40.93% | 4,278 | 5.12% | 535 | 10,452 |
| Saguache | 54.99% | 1,307 | 36.22% | 861 | 8.79% | 209 | 2,377 |
| San Juan | 55.19% | 255 | 39.39% | 182 | 5.42% | 25 | 462 |
| San Miguel | 68.35% | 2,226 | 26.71% | 870 | 4.94% | 161 | 3,257 |
| Sedgwick | 21.72% | 262 | 70.73% | 853 | 7.55% | 91 | 1,206 |
| Summit | 60.33% | 6,957 | 35.08% | 4,046 | 4.59% | 529 | 11,532 |
| Teller | 28.03% | 3,158 | 65.12% | 7,337 | 6.85% | 772 | 11,267 |
| Washington | 10.05% | 237 | 87.15% | 2,055 | 2.80% | 66 | 2,358 |
| Weld | 32.80% | 29,785 | 60.37% | 54,823 | 6.83% | 6,203 | 90,811 |
| Yuma | 11.92% | 512 | 85.65% | 3,678 | 2.43% | 104 | 4,294 |
Counties that flipped from Democratic to Republican
* Chaffee (largest municipality: Salida)
* Conejos (largest municipality: Manassa)
* Garfield (largest municipality: Rifle)
* Grand (largest municipality: Granby)
* Larimer (largest municipality: Fort Collins)
* Las Animas (largest municipality: Trinidad)
* Mineral (largest municipality: Creede)

#### By congressional district

Gardner won 4 of 7 congressional districts.
| District | Gardner | Udall | Representative |
| 1st | 29.39% | 65.67% | Diana DeGette |
| 2nd | 40.07% | 55.24% | Jared Polis |
| 3rd | 53.94% | 40.58% | Scott Tipton |
| 4th | 61.95% | 32.13% | Ken Buck |
| 5th | 61.8% | 32.14% | Doug Lamborn |
| 6th | 49.16% | 45.58% | Mike Coffman |
| 7th | 43.45% | 49.9% | Ed Perlmutter |