

Artur Davis, representing Alabama's Seventh Congressional District, will run for governor of Alabama in 2010. Davis's district leans heavily Democratic. According to the Cook Political Report, 'Its boundaries all but ensure that an African-American Democrat will succeed four-term Rep. Artur Davis.'
Marion Berry, representing Arkansas' First Congressional District will retire in 2010. The Cook Political Report rates this a 'Lean Republican' district, noting its partisan voter index (PVI) is +8 (toward Republican presidential candidates in the past two elections above the national average).
Vic Snyder, of Arkansas' Second Congressional District is planning to retire in 2010. The Cook Political Report rates this a 'Lean Republican' district, with a PVI of +5.
Diane Watson, of California's 33rd Congressional District, announced that she will not seek re-election to the seat she has held since 2001 in order to spend more time with her elderly mother. Watson's district is staunchly Democratic. According to the Cook Report, 'An exclusively urban district that gave President Obama 87 percent of the vote isn't a place where Republicans can compete.'
Kendrick Meek, representing Florida's 17th Congressional District, in running for the Senate seat bing vacated by Republican Mel Martinez. Meek's district leans heavily Democratic. According to the Cook Report, "This is the most Democratic district in Florida and one of the few open seats House Democrats don’t have to lose any sleep over."
Neil Abercrombie, representing Hawaii's First Congressional District since 1991, will run for governor of Hawaii in the 2010 election. The Cook Political Report rates this a 'Lean Democratic' district, with a PVI of +11.
Brad Ellsworth, of Indiana's Eighth Congressional District, will run for a Senate seat being vacated by Democrat Evan Bayh. Though Ellsworth is a Democrat, his district voted Republican in the last two presidential elections, with a PVI of +8. The Cook Political Report rates this a 'Lean Republican' district.
Dennis Moore, representing Kansas' Third Congressional District plans to retire at the end of his term. His district voted narrowly Republican in the last two presidential elections, with a PVI of +3. The Cook Political Report rates this a 'Lean Republican' district.
Charlie Melancon, of Louisiana's Third District, is challenging incumbent Republican David Vitter (R) in the 2010 Senate election. Melancon's district has leaned Republican in recent presidential elections. The Cook Political Report rates this a 'Likely Republican' district.
Paul Hodes, from New Hampshire's Second Congressional District, is running for Senate in 2010 for a seat being vacated by Republican senator, Judd Gregg. His district voted Democratic in the 2004 and 2008 presidential elections. The Cook Political Report rates this a 'Toss Up' district.
Joe Sestak, of Pennsylvania's Seventh Congressional District, will run for Senate in 2010. His district has leaned Democratic in the last two presidential elections, but only slightly. The Cook Political Report rates this a 'Toss Up' district.
Patrick Kennedy, representing Rhode Island's First Congressional District, has announced he will retire at the end of his term. Kennedy's district has voted Democratic in the two most recent presidential elections, with a PVI of +13. The Cook Political Report says this is a 'Kennedy open seat Democrats shouldn’t have to fret about.'
Bart Gordon, of Tennessee's Sixth Congressional District, will retire after year. His district has leaned Republican, with a PVI +13, in the two most recent presidential elections. The Cook Political Report rates this a 'Likely Republican' district.
John Tanner, representing Tennessee's Eighth Congressional District, will retire after 2010. His district has voted Republican in the last two presidential elections, with a PVI of +6.
Brian Baird, of Washington's Third Congressional District, will retire after this year. His district was evenly split in support for Republican and Democratic candidates in the last two presidential elections. The Cook Political Report rates this a 'Toss Up' district.
Bill Delahunt, representing Massachusetts' 10th Congressional District, will retire after 2010. Delahunt's district has leaned Democratic PVI of +5 in the last two presidential elections. According to the Cook Report, 'This seat could easily move to the Toss Up column.'
Rep. Bart Stupak (D) of Michigan will not seek a 10th term in office. He represents Michigan's First Congressional District and was targeted by 'tea party' activists for his vote in favor of healthcare reform. In the 2004 presidential election, his district went for President Bush. In 2008, President Obama won by a slim margin. Here, Stupak speaks about health care and NAFTA during a conference on Capitol Hill on March 4. Manuel Balce Ceneta/AP
Rep. David Obey, a 20-term congressman from Wisconsin, announced May 5 that he would not seek reelection in 2010. The Seventh Congressional District has a +3 rating for Democrats, according to The Cook Political Report's partisan voting index. J. Scott Applewhite/AP