Independent Bernie Sanders, the Senate's only self-described socialist, is expected to sail to a second term over Republican John MacGovern, a former Massachusetts state representative and unsuccessful congressional candidate.

Virgina: Former Gov. Tim Kaine (D) vs. former Gov./Sen. George Allen (R)

Open seat -- Sen. Jim Webb (D) is retiring

Republican George Allen is fighting hard to win back the seat he lost six years ago to now-retiring Democratic Sen. Jim Webb. A strong Democratic wave, along with a gaffe caught on tape that became infamous on YouTube, stripped Allen of what was expected to be his second term (and perhaps a launching pad to the 2008 GOP presidential nomination). He now faces Democratic nominee Tim Kaine, another former governor, in one of the marquee Senate races of 2012.

Polls remain close. Barack Obama's win in Virginia in 2008 and the strong play he's making for the state in 2012 have given Kaine organizational support. Allen has run ads linking Kaine, the chairman of the Democratic National Committee at the start of the Obama administration, to the president and to looming budget cuts. Kaine, in turn, has run ads tying Allen to George W. Bush's economic policies and that he's wrong on women's issues.

Both candidates have seen their leads grow and shrink with the presidential candidates. It's very likely the winner of the Senate seat will be a member of the same party of the presidential candidate who wins Virginia's 13 electoral votes.

Washington: Sen. Maria Cantwell (D) vs. Michael Baumgartner (R)

Democrat Maria Cantwell is expected to win a third term in November. She faces Republican state Sen. Michael Baumgartner.

West Virginia: Sen. Joe Manchin (D) vs. John Raese (R)

No, we did not forget to update this section from 2010. Democrat Joe Manchin once again faces Republican businessman John Raese in the contest to win his first full term. Manchin has proven his independence from the president and faces a much easier race this time to win in November.

Wisconsin: Rep. Tammy Baldwin (D) vs. former Gov. Tommy Thompson (R)

Open seat -- Sen. Herb Kohl (D) is retiring

Former Gov. Tommy Thompson won a tough Republican primary to take on seven-term Democratic Rep. Tammy Baldwin for retiring incumbent Herb Kohl's Senate seat. Thompson's attacks on Baldwin as being too liberal haven't had the impact he was hoping. The polls are very close, but Baldwin has pulled slightly ahead recently, though not outside the margin of error.

Unless vice presidential candidate and native son Paul Ryan brings out strong turnout for the party, the state's historic Democratic tilt in presidential elections could help Baldwin succeed to becoming the first openly gay senator.

Wyoming: Sen. John Barrasso (R) vs. Tim Chesnut (D)

Republican John Barrasso is expected to win a second term in November. He faces Democratic nominee Tim Chesnut, an Albany County commissioner.