As polls began to close in the East and Midwest, the contentious Senate race in Virginia is too close to call.
In preliminary exit polls, Jim Webb — a best-selling author, Vietnam Marine and former Republican — was just ahead of the incumbent, Sen. George Allen. Once a long shot, Webb has made the race a toss-up. Allen was a presidential contender a year ago, but now he's fighting for his life after a series of campaign gaffes and errors.
Also in Virginia, voters have passed an amendment banning same-sex marriage.
Preliminary CBS News exit polling data suggests that like Virginia, most other very tight races, including those in Tennessee and Missouri, are very close, with Democrats are maintaining a slight edge.
The past few months have been an uphill battle for the Democrats, who must gain six seats to make a Senate majority. After significant gains by the Democrats against GOP incumbents this fall, they are knocking on the Senate door.
Democrats appealed to voter weariness with the war, GOP White House and recent corruption scandals as voters went to the polls to fill 33 of the Senate's 100 seats. Democrats need a net pickup of six to recapture the majority that they last briefly exercised in 2001-2002. Seventeen seats now held by Democrats and 15 seats now filled by Republicans, including the Tennessee post of retiring Majority Leader Bill Frist, are up for grabs.
Conventional wisdom says the Democrats are well-positioned to pick up seats in Ohio, Rhode Island and Pennsylvania. They are leaning behind in Tennessee, which was a toss-up a week ago. If they lose there and hold all their current seats, Democrats would then need to win all three remaining toss-ups: Virginia, Missouri and Montana.
Meanwhile, Republicans' reign over the House of Representatives faced a serious challenge Tuesday as a surge of Democratic support sparked by voter outrage over the Iraq war and disapproval of President Bush and Congress gave Democrats a chance to regain a majority in the House for the first time since 1994.
But while only one Republican candidate has a strong chance at booting out a Democratic incumbent, Republicans are guardedly optimistic that they will retain control — barely — as the votes come in.
That said, anything could happen. So what are the races to watch when the polls start to close tonight? CBS News' Gloria Borger reports that most eyes are on 10 battleground states, eight of which are currently held by Republicans.
Keep in mind that Democrats last controlled the Senate in 2002. Republicans now control 55 seats in the 100-member chamber. Two Independents, Sen. Bernie Sanders, I-Vt., and likely Connecticut race winner Joseph Lieberman will caucus with the Democrats and count toward Democratic tallies. If there's a 50-50 split in the Senate, Vice President Dick Cheney serves as the tiebreaker, meaning the majority leader and committee chairs would be Republican and any split-down-the-middle votes would be decided by Cheney.
Undoubtedly, the night will have some surprises. Arizona Republican Sen. Jon Kyl could be in for an unexpectedly close race, some observers say. So could Democratic Sen. Debbie Stabenow from Michigan.Sen. Jim Talent of Missouri is locked in a dead heat with his Democratic opponent. Exit polls show that Missouri voters are rating the economy as a very important issue in determining their vote. Polls during the past two weeks show Talent, a first-term Republican, narrowly trailing challenger Claire McCaskill, a former attorney and Jackson County prosecutor. CBS News reporter Steve Futterman met McCaskill while she was shaking hands with shoppers at a St. Louis supermarket. "It feels close," McCaskill told Futterman. "We are going to treat it like its close and we're going to campaign that way until 7 o'clock tomorrow night." The winner may not be known till long after that.In Ohio, one of the tight races that could be an early indicator of Democratic momentum, Sen. Mike DeWine is trailing his Democratic challenger, seven-term Rep. Sherrod Brown, in CBS News exit polls. The last time a Democrat won an Ohio Senate race was 1992, making this a possible upset to watch. The Democrats are counting on a win here.In Tennessee's race to replace retiring Senate Majority Leader Bill Frist, Republican Bob Corker seems to be pulling away from Democratic Rep. Harold Ford Jr. Corker leads by 12 points in the latest poll from the Chattanooga Times Free Press & Memphis Commercial Appeal. A steamy ad produced by the Republican National Committee made national headlines for its steamy — and allegedly racist — content. In the ad, a young white actress talks about meeting Ford, a 36-year-old bachelor who is black, "at the Playboy party." At the end of the ad, she winks and says to the camera, "Harold, call me." Both candidates denounce the ad as tacky, but the ad became the poster child for an especially dirty campaign season.Among Democratic incumbents, only Sen. Robert Menendez of New Jersey was considered in any real danger. He held a 48-43 percent edge over Republican challenger Tom Kean Jr. in a new Quinnipiac University poll. Other recent polls have given the Democrat as much as a 10-point lead. Lieberman is now leading securely in polls against cable executive and newcomer to the national political scene Ned Lamont, who won Connecticut's Democratic primary and caused the one-time presidential candidate to change parties. The saga comes to a close when voting stops at 8 p.m.In the battle for Maryland's open Senate seat, Democrat Ben Cardin, a Jewish U.S. Representative who had held a comfortable lead over Republican Michael Steele, a black Catholic Lt. Gov., now leads by just 3 points in the latest Mason-Dixon poll. A SurveyUSA poll shows the race even. This is a Democratic seat, so if Cardin loses, the Democratic hunt for the Senate gets harder.GOP Sen. Rick Santorum and of Pennsylvania is a legend for his staunch conservative views, and a favorite target of GOP-bashers. Now his pro-life Democratic opponent, state Treasurer Robert Casey Jr., appears poised to handily take down Santorum. Also, his moderate views will be some to watch once the composition of the Senate is settled.Polls close at 9 p.m. in Rhode Island, where Republican Sen. Lincoln Chafee, who had been written off by some observers, has narrowed the gap with Democratic challenger Sheldon Whitehouse to 3 points in the latest USA Today/Gallup poll. A Mason-Dixon poll showed Chafee within one percentage point of Whitehouse.The last of the big races close their voting booths at 10 p.m.. In Montana, where Republican Sen. Conrad Burns had been struggling, polls are inconclusive, either showing Burns and Democrat Jim Tester tied (Mason-Dixon), or Tester with a 9-point lead (USA Today/Gallup). Monday, a Burns spokesman dismissed the USA Today/Gallup poll as inaccurate and said the campaign was revoking one newspaper's credentials to attend Burns' election night event in Billings because it wrote about the poll.
By Christine Lagorio
© 2006 CBS Interactive Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.