At this hour, the polls were scheduled to close in some 25 states -- including many with crucial contests that will help determine who controls the next Congress.
The midterm elections have been unusually hard-fought in 2006. President Bush, suffering from low approval ratings and voters' disappointment about the war in Iraq, was battling for his party. But Democrats were optimistic about significant gains.
Democrat Ted Strickland is projected to win the governor's race in Ohio.
Democrat Robert Byrd is keeping his Senate seat in West Virginia.
NPR also projects that Bernie Sanders will win the Senate seat from Vermont -- and Republican Dick Lugar will win in Indiana. He was not opposed by a Democrat.
Voters are choosing 435 members of the House, 33 senators and 36 governors -- and according to NPR's Mara Liasson, electorate is focusing on the central issue of Iraq at the polls.
A critical Senate race is in Tennessee. There, Rep. Harold Ford (D) is running against Republican Bob Corker. The two have been engaged in an intense race to replace retiring Senate Majority Leader Bill Frist.
NPR's Scott Horsley is covering Bob Corker in his hometown of Chattanooga, where he was mayor.
And NPR's Audie Cornish is with Harold Ford's campaign in Memphis.
In Missouri, there is a fierce Senate race between Republican incumbent Jim Talent and Democrat Claire McCaskill.
NPR's Frank Langfitt is at McCaskill's headquarters in downtown St. Louis. He reports heavy turnout, perhaps spurred by a state stem-cell referendum.
NPR's Wade Goodwin is at Jim Talent's headquarters near the St. Louis airport.
And in New Jersey, a battle royale has been waged between Senate hopefuls Robert Menendez and Thomas Kean Jr.
NPR's Ari Shapiro is at Democratic headquarters in Washington.