Voters in 12 states cast ballots Tuesday in contests that will determine the fate of a Senate incumbent in Arkansas, decide the matchups for high-stakes races in Nevada and California and settle a nasty gubernatorial primary in South Carolina. A look at the contests:
ARKANSAS (Polls close at 8:30 p.m. EDT)
Two-term Sen. Blanche Lincoln, a centrist Democrat, is fighting for her political life against Lt. Gov. Bill Halter. The two were forced into a runoff for the party nomination after neither captured 50 percent of the vote in the May 18 primary. Unions and other outside groups have spent millions in the state to influence the outcome.
CALIFORNIA (Polls close at 11 p.m. EDT)
Republican billionaire Meg Whitman has invested more than $70 million of her own fortune in the governor's race against state insurance commissioner Steve Poizner, a wealthy former businessman who has put $24 million into his campaign. The likely winner of the Democratic nomination is Attorney General Jerry Brown, who was governor in the 1970s and 1980s.
Carly Fiorina, a former Hewlett Packard Co. chief executive, is leading in some polls over her GOP opponents for Senate: former U.S. Rep. Tom Campbell and state Assemblyman Chuck DeVore, a tea party favorite. The winner will challenge Democratic Sen. Barbara Boxer.
The congressional race in Southern California's 36th District features contrasting Democratic candidates Rep. Jane Harman – who belongs to the Blue Dog group of conservative Democrats – and Marcy Winograd, co-founder of the Los Angeles chapter of Progressive Democrats of America. In 2006, Harman beat Winograd with 62 percent of the vote.
NEVADA (Polls close at 10 p.m. EDT)
Gov. Jim Gibbons could potentially be the first sitting governor to lose a nominating contest in the state in 100 years. He's had a tumultuous first term that included a nasty public divorce and allegations of infidelity. Polls have found Gibbons trailing GOP front-runner Brian Sandoval by double digits.
Three Republicans are in a bruising fight for the chance face Senate Majority Leader Harry Reid. Tea party favorite Sharron Angle has recently been running ahead of former Nevada GOP Chairwoman Sue Lowden and Las Vegas businessman Danny Tarkanian.
SOUTH CAROLINA (Polls close at 7 p.m. EDT)
Republican state Rep. Nikki Haley is hoping to become the state's first female governor. The race has turned nasty with allegations of infidelity, which she denies. In some polls, Haley is edging out her GOP challengers, including Rep. Gresham Barrett, Lt. Gov. Andre Bauer and Attorney General Henry McMaster. Of the three Democratic gubernatorial candidates, state Sen. Vincent Sheheen has spent the most money so far. All are vying to succeed the term-limited Gov. Mark Sanford in the Republican-leaning state.
Democrats pick a challenger to Republican Sen. Jim DeMint.
South Carolina Republican Rep. Bob Inglis is in a tough race to keep the seat he's held for six terms. His challengers have made the primary a referendum on his 2008 vote to bail out the nation's banking industry. His race, as well as GOP gubernatorial primary, could end up in a June 22 runoff.
IOWA (Polls close at 10 p.m. EDT)
Iowa has a three-way Republican primary for the right to oppose Democrat Chet Culver, considered one of the nation's most vulnerable governors. Polls suggest former Gov. Terry Branstad leading over businessman Bob Vander Plaats and state Rep. Rod Roberts. Democrats choose a challenger to Sen. Charles Grassley.
MAINE (Polls close at 8 p.m. EDT)
The primary races for governor are wide-open, with no clear front-runners to replace term-limited Democratic Gov. John Baldacci. A seven-way Republican primary includes tea party favorite Paul LePage. Businesswoman Rosa Scarcelli has staked out the right and the outsider's role in the four-way Democratic race. The other three are government insiders – Senate President Libby Mitchell, former Attorney General Steve Rowe and Pat McGowan, a former legislator who also served in Baldacci's Cabinet.
NORTH DAKOTA (Polls at 8 p.m. and 9 p.m. EDT)
Officials in both parties say Sen. Byron Dorgan's retirement gives Republicans their best opportunity to pick up a seat in the Senate. Republican Gov. John Hoeven is the leading candidate.
SOUTH DAKOTA (Polls close at 8 p.m. and 9 p.m. EDT)
Democrats failed to find a candidate to challenge Republican Sen. John Thune, a popular politician who is seeking a second term in the Senate.
VIRGINIA (Polls close at 7 p.m. EDT)
Republicans face critical choices about nominees as they look to win back the three Virginia U.S. House seats lost in the Democrats' 2008 sweep. The GOP has its eye on Rep. Tom Perriello's 5th Congressional District seat, since he won in 2008 by just 727 votes. Seven candidates are vying for the nomination, with no clear front-runner.
GEORGIA (Polls close at 7 p.m. EDT)
In north Georgia, Tom Graves hopes his involvement with the Atlanta Tea Party Patriots will help him defeat Lee Hawkins, another conservative, in a runoff to fill a vacant House seat in a heavily Republican district. Rep. Nathan Deal resigned to run for governor.
NEW JERSEY (Polls close at 8 p.m. EDT)
Members of the House faced challenges in seven of the state's 13 congressional districts but no upsets were expected. The tea party movement created a crowded field on the Republican side, with some candidates, including former NFL star Jon Runyan, endorsed by both the GOP and a tea party group.
MONTANA (Polls close at 10 p.m. EDT)
Republican Rep. Denny Rehberg is the front-runner in his re-election bid, though he has challengers from both the left and the right.