Question: The 2012 United States Senate election in Nevada ended in a narrow win for which incumbent Republican?

full_context: Document 1: Joe Heck: Joseph John “Joe” Heck (born October 30, 1961) is an American politician, physician, and U.S. Army Brigadier General who had served as the U.S. Representative for Nevada's 3rd congressional district from 2011 to 2017. Heck, a member of the Republican Party, is a board-certified physician and served as a Nevada State Senator from 2004-08. He ran unsuccessfully against Democrat Catherine Cortez Masto in the general election for the open Nevada United States Senate seat in 2016. In the same year, Heck made headlines by joining a long list of Republicans who opposed the GOP nominee for President, Donald Trump.
Document 2: Nevada gubernatorial election, 2006: The 2006 Nevada gubernatorial election was held on November 7, 2006. Incumbent Governor Kenny Guinn could not run due to term limits. Republican Congressman Jim Gibbons defeated Democratic State Senator Dina Titus.
Document 3: Dean Heller: Dean Arthur Heller (born May 10, 1960) is the senior United States Senator from Nevada and a member of the Republican Party. He was elected in Nevada to that state's open U.S. Senate seat in 2012.
Document 4: United States Senate election in Indiana, 2012: The 2012 United States Senate election in Indiana took place on November 6, 2012, concurrently with the U.S. presidential election as well as other elections to the United States Senate, House of Representatives, and various state and local elections. Incumbent Republican U.S. Senator Richard Lugar ran for re-election to a seventh term, but was defeated in the primary by Tea Party-backed Richard Mourdock. Congressman Joe Donnelly, a moderate Democrat from Indiana's 2nd Congressional District, received his party's nomination after running unopposed in the primary contest, and then defeated both Mourdock and Libertarian Andrew Horning in the general election.
Document 5: Deb Fischer: Debra Strobel Fischer (born March 1, 1951) is the senior United States Senator from the state of Nebraska. Previously, she was a two-term member of the Nebraska Legislature, representing the 43rd District. She defeated former United States Senator Bob Kerrey in the election held on November 6, 2012, and assumed one of Nebraska's two Senate seats in January 2013.
Document 6: United States Senate election in Wyoming, 2012: The 2012 United States Senate election in Wyoming took place on November 6, 2012, alongside a U.S. presidential election as well as other elections to the United States Senate and House of Representatives and various state and local elections. Incumbent Republican U.S. Senator John Barrasso won re-election to a first full term.
Document 7: John Hoeven: John Henry Hoeven III (born March 13, 1957) is an American politician and the senior United States Senator from North Dakota, in office since 2011. A member of the North Dakota Republican Party, he previously served as the 31st Governor of North Dakota from December 2000 to December 2010. Hoeven was elected to the U.S. Senate in the November 2, 2010 general election. He replaced junior Senator Byron L. Dorgan, who chose not to seek re-election. Hoeven became the senior Senator in 2013 after Kent Conrad retired and was replaced by Heidi Heitkamp, who was once Hoeven's opponent for the Governor's office.
Document 8: Shirley Breeden: Shirley Breeden is a Democratic member of the Nevada Senate, representing Clark County District 5 (map) since 2009. She won her first term in 2008, when she narrowly upset incumbent Republican Joe Heck.
Document 9: Sharron Angle: Sharron Elaine Angle (born Sharron Elaine Ott; July 26, 1949) is an American politician who served as a Republican member of the Nevada Assembly from 1999 to 2007. She ran unsuccessfully as the 2010 Republican nominee for the U.S. Senate seat in Nevada, garnering 45 percent of the vote. On September 15, 2013 she was unanimously elected the fifth President of the National Federation of Republican Assemblies, and resigned in 2016 to run again for the Nevada U.S. Senator position being vacated by Harry Reid but failed to win the Republican primary.
Document 10: United States Senate election in Nevada, 2012: The 2012 United States Senate election in Nevada was held on Tuesday, November 6, 2012, alongside 33 other elections to the United States Senate in other states, as well as elections to the United States House of Representatives, and the 2012 United States presidential election. The primary election was held June 12, 2012. Incumbent Republican U.S. Senator Dean Heller, who was recently appointed to this seat left vacant by resigning U.S. Senator John Ensign, was narrowly elected to his first full term over Congresswoman Shelley Berkley.
Document 11: United States Senate election in Utah, 2012: The 2012 United States Senate election in Utah took place on November 6, 2012, concurrently with the 2012 U.S. presidential election as well as other elections to the United States Senate and House of Representatives and as various state and local elections. Incumbent Republican U.S. Senator Orrin Hatch won re-election to a seventh term against former state Senator and IBM executive, Scott Howell the Democratic candidate.
Document 12: United States Senate election in Arizona, 2012: The 2012 United States Senate election in Arizona was held on November 6, 2012, alongside a presidential election, other elections to the United States Senate in other states, as well as elections to the United States House of Representatives and various state and local elections. Incumbent Republican U.S. Senator Jon Kyl, the Senate Minority Whip, decided to retire instead of running for re-election to a fourth term. Republican U.S. Representative Jeff Flake won the open seat.
Document 13: List of United States Senators from Nevada: Nevada was admitted to the Union on October 31, 1864. Its current senators are Democrat Catherine Cortez Masto (Class 3) and Republican Dean Heller (Class 1).
Document 14: United States Senate election in Arizona, 1962: The 1962 United States Senate election in Arizona took place on November 6, 1962. Incumbent Democratic U.S. Senator Carl Hayden ran for reelection to a seventh term, defeating Republican nominee State Senator Evan Mecham in the general election. Mecham became Governor of Arizona more than two decades later, and was subsequently impeached from office.
Document 15: United States Senate election in Virginia, 2012: The 2012 United States Senate election in Virginia took place on November 6, 2012, concurrently with the 2012 U.S. presidential election as well as other elections to the United States Senate and House of Representatives and various state and local elections. Incumbent Democratic U.S. Senator Jim Webb decided to retire instead of running for re-election to a second term. Former Governor of Virginia Tim Kaine was unopposed for the Democratic nomination and the Republican party nominated former Senator and Governor George Allen through a primary on June 12, 2012. Kaine won the open seat.
ground_truth: Dean Arthur Heller