The margin separating Sen. Michael Bennet (D-Colo.) and Republican Ken Buck in Colorado's Senate race was smaller than 9,500 votes Wednesday morning.

With 79 percent of precincts reporting results, Buck was clinging to a slim lead in a race that could be headed for a recount unless the Republican prosecutor pulls away — a scenario that seems unlikely, given that plenty of the vote is still outstanding in Boulder County, a Democratic stronghold.

Neither candidate declared victory Tuesday, with both sides expressing confidence that votes still outstanding would break their way.

In Washington state, Sen. Patty Murray (D-Wash.) leads by just 14,005 votes with 62 percent of predicts reporting, a margin small enough that it could drag the contest out past Wednesday.

Addressing supporters late Tuesday, Murray predicted that her lead over Republican Dino Rossi would grow as votes continued to be counted.

Just over 54 percent of the vote has been counted in Murray's stronghold of King County in the western part of the state. That's where Democrats expect Murray to make gains.

There is the strong possibility that there are thousands of ballots still outstanding — as long as the ballot is postmarked by midnight on Election Day, it will be counted, so state elections officials will have to wait for outstanding ballots if the race remains this tight.

Rossi is also no stranger to Washington state recounts. He lost a race for governor in 2004 by less than 200 votes after a recount fight made it all the way to the state's highest court.

While the drama is high in both Colorado and Washington state, the Senate majority is already settled.

Democrats ended any hope Republicans might have had to seize control of the upper chamber Tuesday with wins in Nevada, California, West Virginia and Connecticut.