With the polls closed for less than an hour and roughly 200,000 votes counted, state Speaker Jeff Merkley (D) is out in front of Sen. Gordon Smith (R) in Oregon.
According to the Oregon secretary of State, early totals show Merkley leading Smith, 60 percent to 36 percent, while Constitution Party candidate Dave Brownlow had 4 percent of the vote.
Meanwhile, CNN has declared Sen. Roger Wicker (R-Miss.) the winner in his race with ex-Gov. Ronnie Musgrove (D).
All told, Democrats have picked up five Senate seats so far, giving them 56 votes in the Senate with Oregon and three other states still in play: Alaska, Minnesota and Georgia.
In Alaska, polls will close at 1 a.m. EST, and election officials have not begun to count the votes in the much-anticipated contest between recently convicted Sen. Ted. Stevens (R) and Anchorage Mayor Mark Begich (D).
In Minnesota, with 1,761 of 4,130 precincts reporting, Sen. Norm Coleman (R-Minn.) was running neck-and-neck with comedian Al Franken (D). Franken had 42 percent to Colemans 41 percent, according to the Minnesota secretary of State. Former Sen. Dean Barkley (I) has about 15 percent.
In Georgia, Sen. Saxby Chambliss (R) is poised to defeat state Rep. Jim Martin (D) and avoid a Dec. 2 runoff. With 87 percent of precincts reporting, Chambliss was in front, 53 percent to 44 percent. Libertarian candidate Allen Buckley had 4 percent of the vote.
So far tonight, Democrats have knocked off incumbent Sens. Elizabeth Dole (R-N.C.) and John Sununu (R-N.H.) and won open-seat contests in Colorado, New Mexico and Virginia.
Democrats were also successfully defending Sen. Mary Landrieu (D-La.) at last glance. With 3,807 of 3,956 precincts in, Landrieu was defeating state Treasurer John Kennedy (R), 51 percent to 47 percent, according to the Louisiana secretary of State.
Republicans also successfully played defense in the Bluegrass State, where Minority Leader Mitch McConnell (R-Ky.) defeated wealthy businessman Bruce Lunsford (D), and in Maine, where Sen. Susan Collins (R) topped Rep. Tom Allen (D).