Democrats seeking re-election (16 seats)
Dianne Feinstein of California
Four-term Senator Dianne Feinstein was re-elected with 59% of the vote in 2006. She will be 79 years old in 2012.
At a rally for Barbara Boxer in October 2010, Feinstein hinted that she will be running for re-election.
Possible GOP Nominees include 2010 GOP Senate nominee Carly Fiorina, state Assemblyman Chuck DeVore, and Congressman Darrell Issa. 2010 Republican Gubernatorial nominee Meg Whitman has ruled out a Senate Run.
Tom Carper of Delaware
Two-term Senator Tom Carper was reelected with 70% of the vote in 2006. He will be 65 years old in 2012. Carper will seek re-election.
Possible Republican candidates include political commentator and 2010 Republican U.S. Senate nominee Christine O'Donnell and Businesswoman and 2010 Republican U.S. Congress primary nominee Michele Rollins.
Bill Nelson of Florida
Two-term Senator Bill Nelson was reelected with 60% of the vote in 2006. He will be 70 years old in 2012. Nelson will seek re-election. Plant City Republican Mike McCalister has announced his candidacy, as has Florida State Senate President Mike Haridopolos and former Senator George LeMieux.
Other potential Republican candidates include Congressman Vern Buchanan, Lieutenant Governor Jennifer Carroll, and former state House Majority Leader Adam Hasner.
A poll conducted in July, 2010 showed Nelson leading LeMieux 49-28% with 23% undecided.
Ben Cardin of Maryland
First-term Senator Ben Cardin was elected with 54% of the vote in 2006 against former Maryland Lt. Gov. Michael S. Steele. He will be 69 years old in 2012. According to a Public Policy Polling survey conducted of 569 voters from July 10–12, 2010, in a potential rematch of 2006, Cardin leads Steele 58% to 28%. In a generic matchup, Cardin leads with 51%, to an unknown generic Republican at 33%.
After losing reelection for the RNC chairmanship, Steele may seek a rematch with Cardi]
Debbie Stabenow of Michigan
Two-term Senator Debbie Stabenow was re-elected in 2006 with 57% of the vote to 41% for Oakland County Sheriff and former State Senate Majority Leader Michael Bouchard after narrowly defeating Republican incumbent Spencer Abraham in 2000.
Republican Conservative Constitutionalist and Tea Party Activist Chad Dewey announced his intent to run in the 2012 election while attending the Tax Day Tea Party event in Washington D.C. on April 15, 2010.[ Also libertarian activist Scotty Boman is considering a run as a Republican.
Recent polling shows Stabenow leading all potential opponents.
Former Michigan Secretary of State Terri Lynn Land is looking at a possible run.
Amy Klobuchar of Minnesota
First-term Senator Amy Klobuchar was elected with 58% of the vote in 2006. Senator Klobuchar's approval ratings, last reported at 59%, have steadily risen since her election in November 2006. Her quick response to the I-35 bridge collapse in her home city of Minneapolis and her travels around the state have solidified the senator's popularity with the citizens of Minnesota. On March 12, 2010, a Rasmussen poll indicated 67% of Minnesotans approved of the job she was doing.
Claire McCaskill of Missouri
In this bellwether state, first-term Senator Claire McCaskill was elected with 49.6% of the vote in 2006, narrowly defeating then-incumbent Jim Talent. McCaskill will seek re-election in 2012, so far with no prominent Democrat primary challenger.
Former State Treasurer Sarah Steelman and former U.S. House candidate and attorney Ed Martin are the only Republicans so far to have declared their bid for the Republican nomination. Jim Talent has declined to run again. Other potential Republican candidates include Congressman Todd Akin and Ann Wagner, former Chair of the Missouri Republican Party and former Ambassador to Luxembourg.
A survey by PPP on December 1, 2010 showed McCaskill with an approval rating of 43%, with 44 % disapproving. The same study showed her leading Steelman by 1% in a possible 2012 matchup (with a ±4.3% margin of error).
Jon Tester of Montana
First-term Senator Jon Tester was elected with 49.2% of the vote in 2006, defeating incumbent Conrad Burns. Tester will seek re-election. Republican Congressman Denny Rehberg has announced his candidacy for the seat.
Former Republican Montana Governor Marc Racicot is also looking at running.
Ben Nelson of Nebraska
Two-term Senator and former Governor Ben Nelson was re-elected with 64% of the vote in 2006. He will be 71 years old in 2012. Nelson has decided to seek a third term. Republican State Attorney General Jon Bruning has announced his candidacy.
Pundits and analysts have suggested Nelson will be one of the most vulnerable incumbents in 2012 after he secured deals to exempt Nebraska from new Medicaid payments, ease excise taxes on home state health insurance companies, and broker abortion deals in the Senate healthcare bill.
Treasurer Don Stenberg may run on the Republican ticket. Nebraska Governor Dave Heineman has announced he will not run.
Bob Menendez of New Jersey
First-term Senator Bob Menendez became the first Hispanic Senator to represent New Jersey in January 2006 when Former Senator Jon Corzine appointed him to the office after having resigned to become Governor, following his election to said office in November 2005. In November 2006 Menendez easily defeated Republican Tom Kean, Jr., son of popular former Governor and 9/11 Commission Chairman Tom Kean and was elected to a full term. He will be 58 years old in 2012.
In November 2009, former CNN Anchor Lou Dobbs was seriously considering a challenge to Menendez as either a Republican or Independent.
Kirsten Gillibrand of New York
Two-term Senator Hillary Rodham Clinton was re-elected with 67% of the vote in 2006. She narrowly lost the 2008 Democratic Presidential nomination to Barack Obama. She resigned on January 21, 2009 when the Senate confirmed her as Secretary of State. On January 23, Governor David Paterson appointed Congresswoman Kirsten Gillibrand to the seat. Gillibrand won a special election in 2010 with 61.2% of the vote. Gillibrand will seek re-election
Sherrod Brown of Ohio
First-term Senator Sherrod Brown was elected with 56% of the vote in 2006, defeating then-incumbent Mike DeWine, whose popularity suffered due to scandals involving former Republican Governor Bob Taft and ex-Congressman Bob Ney. A poll conducted June 26–27 by Public Policy Polling shows that 45% of voters would vote to re-elect Brown, while 41% would vote to replace him.
Brown will seek re-election in 2012 when he will be 60 years old. Congressman Jim Jordan, Lieutenant Governor Mary Taylor, Congressman Steve LaTourette and Eric LaMont Gregory have all been named as possible Republican contenders. Dave Zanotti of the Ohio Roundtable has also been mentioned as a possible contender, running as an independent.
Bob Casey, Jr. of Pennsylvania
First-term Senator Bob Casey, Jr., the son of popular former Governor Bob Casey, was elected with 58.7% of the vote in 2006, defeating then-incumbent Rick Santorum. He was the first Democrat elected to a full term in the U.S. Senate from Pennsylvania since 1962. A poll conducted by Municipoll February 21–23, 2011 showed that in a Casey-Santorum rematch, Casey leads 50-38. Casey will seek re-election.
Former Senate staffer Marc Scaringi has announced his candidacy as a Republican.
Sheldon Whitehouse of Rhode Island
First-term Senator Sheldon Whitehouse was elected with 53.5% of the vote in 2006, defeating then-incumbent Lincoln Chafee by 6 percentage points. Whitehouse will seek reelection.
Potential Republican Candidates include Former Governor Donald Carcieri, 2010 Republican nominee for Governor John Robitaille, and Warwick mayor Scott Avedisian.
Maria Cantwell of Washington
Two-term Senator Maria Cantwell was re-elected with 57% of the vote in 2006 over Republican Mike McGavick. A poll conducted by Public Policy Polling July 27-August 1, 2010 of 1,204 voters had Cantwell leading in two potential matchups. In a matchup with Republican Congressman Dave Reichert, Cantwell led 47% to 41%. In a matchup with Republican Congresswoman Cathy McMorris Rodgers, Cantwell led 49% to 37%. Susan Hutchison, who was a 2009 candidate for King County Executive, has also been mentioned as a possible opponent for Cantwell.
Joe Manchin of West Virginia
Former nine-term Senator Robert Byrd, the longest serving U.S. Senator in history, was re-elected with 64.4% of the vote in 2006. On June 28, 2010, Senator Byrd died at the age of 92, leaving this seat vacant. A special election to fill this seat was held in November 2010, which Democratic Governor Joe Manchin won with 53.5% of the vote. Manchin will be 65 years old in 2012.
Congresswoman Shelley Moore Capito is the GOP favorite to run for the seat.
Democrat with undeclared intentions (1 seat)
Herb Kohl of Wisconsin
Four-term Senator Herb Kohl, owner of the NBA's Milwaukee Bucks, was re-elected with 67% of the vote in 2006. He will be 77 years old in 2012. Kohl will determine whether he should seek re-election over the next several of months.
Congressman Paul Ryan will not run against Kohl if he seeks re-election but will contemplate running for the Senate if Kohl were to retire