# 2012 Missouri Attorney General election

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The 2012 Missouri Attorney General election was held on November 6, 2012, alongside the presidential and gubernatorial elections. The incumbent Missouri Attorney General Chris Koster, a Democrat, won re-election for a second full term against Republican attorney Ed Martin. As of 2025, this is the last time a Democrat was elected Attorney General of Missouri.

## Background

Koster was originally elected as attorney general in 2008 as a Democrat after switching from the Republican Party. Koster won despite accusations that his campaign violated state law in raising money from multiple committees. He also survived the disclosure that he played a supporting role in a plagiarism episode that damaged Attorney General William L. Webster’s campaign for governor in 1992. Fresh out of law school, Koster worked for Webster, a Republican, as an assistant state attorney general.
He defeated State Representative Margaret Donnelly in the Democratic primary for the nomination for Missouri Attorney General and won against Republican state senator Michael R. Gibbons in the general election, 53%-47%. He was sworn in as attorney general on January 12, 2009, succeeding Jay Nixon, who had served since 1993.

## Timeline

* March 27, 2012 - Filing deadline for Democrats, Republicans and Libertarians
* August 7, 2012 - Primary (gubernatorial and other statewide office) elections
* August 21, 2012 - Filing deadline for other third parties and Independents
* November 6, 2012 - General election.

## Republican primary
### Candidates
#### Declared

* Ed Martin, attorney
* Adam Lee Warren, prosecuting attorney of Livingston County

#### Declined

* Cole McNary, state representative

### Polling

| Poll source | Date(s) administered | Sample size | Margin of error | Ed Martin | Adam Warren | Undecided |
| Public Policy Polling | August 4–5, 2012 | 590 | ± 4.0% | 46% | 17% | 37% |

### Results

100% reporting (3,420 of 3,420 precincts)
Republican primary results :
| Party | Party | Candidate | Votes | % |
| | Republican | Ed Martin | 373,434 | 71.6 |
| | Republican | Adam Lee Warren | 148,432 | 28.4 |
| Total votes | Total votes | Total votes | 521,866 | 100.0 |
Martin, who served as chief of staff for Governor Matt Blunt from 2006 until November 2007, won the Republican primary in a landslide, 72%-28% and become the party's nominee.

## Democratic primary
### Candidates
#### Declared

* Chris Koster, incumbent Attorney General since 2008
Koster was unopposed for the Democratic nomination.

## General election
### Polling

| Poll source | Date(s) administered | Sample size | Margin of error | Chris Koster (D) | Ed Martin (R) | Other | Undecided |
| Mason-Dixon | October 23–25, 2012 | 625 | ± 4% | 51% | 37% | — | 12% |
| Public Policy Polling | October 19–21, 2012 | 582 | ± 4.1% | 48% | 38% | — | 13% |
| Public Policy Polling | August 20, 2012 | 500 | ± 4.4% | 41% | 39% | — | 20% |

### Results

2012 Missouri Attorney General election :
| Party | Party | Candidate | Votes | % | ±% |
| | Democratic | Chris Koster (incumbent) | 1,482,381 | 55.81% | +2.98 |
| | Republican | Ed Martin | 1,081,510 | 40.71% | −6.46 |
| | Libertarian | Dave Browning | 92,465 | 3.48% | N/A |
| Total votes | Total votes | Total votes | 2,668,064 | 100.00% | N/A |
| | Democratic hold | Democratic hold | Democratic hold | Democratic hold | Democratic hold |
On election day, Koster defeated Martin by a wide margin of over 14 percentage points, an increase from his 5% margin of victory in 2008. This is despite Republican Mitt Romney defeating Democratic President Barack Obama in the concurrent presidential election in Missouri, although other incumbent state Democratic officials were re-elected as well. Governor Jay Nixon won re-election by more than 12 percentage points, Senator Claire McCaskill won re-election by over 15 percentage points, and Clint Zweifel won by 5 percentage points. Jason Kander was also elected Secretary of State by just over one percentage point.

#### By congressional district

Koster won 6 of 8 congressional districts, including four that elected Republicans.
| District | Koster | Martin | Representative |
| 1st | 83% | 15% | Lacy Clay |
| 2nd | 51% | 46% | Todd Akin (112th Congress) |
| 2nd | 51% | 46% | Ann Wagner (113th Congress) |
| 3rd | 50% | 46% | Russ Carnahan (112th Congress) |
| 3rd | 50% | 46% | Blaine Luetkemeyer (113th Congress) |
| 4th | 52% | 44% | Vicky Hartzler |
| 5th | 67% | 29% | Emanuel Cleaver |
| 6th | 51% | 45% | Sam Graves |
| 7th | 44% | 52% | Billy Long |
| 8th | 48.0% | 48.3% | Jo Ann Emerson |