By Mark Willen, Senior Political Editor February 22, 2008 Tired of the presidential contest already? Don't fret. There are plenty of other races that'll be at least as interesting. Democrats aren't just hoping to take the White House; they're also hell bent on adding to their majorities in the House and Senate. They almost certainly will -- the only question is, by how much? Count on at least three more in the Senate for sure, with four or five a good bet and even six a possibility. That means something like a 56-44 slant, enough to give Majority Leader Harry Reid a little more breathing room than the 51-49 margin of today, but not enough to shut off a filibuster. He'll still need to pick up a few GOP moderates to hit the magic 60 votes needed to do that. Where will the Democratic gains come from? In Virginia, for starters, where Mark Warner will replace John Warner, who is retiring, and in New Mexico, where Tom Udall is a safe bet to replace Pete Domenici, who is also retiring. Democrats also have strong shots to take the open Republican seat in Colorado (Wayne Allard is calling it quits), and to knock off either or both Minnesota Sen. Norm Coleman or New Hampshire's John Sununu. Plus two other Republicans, Maine's Susan Collins and Oregon's Gordon Smith are going to have to fight to keep their seats. Democrats will also boost their margin in the House, helped by close to 30 GOP retirements, a big fundraising advantage and an unpopular president dragging Republicans down. But it will be tough to score a knockout because many Democratic freshmen were elected in 2006 by narrow margins in close swing districts. A gain of about 15 is most likely, lifting the Democratic advantage to a little better than 245-190.