As the election -- now less than four weeks away -- creeps closer, Democrats are poised to make big gains in the House and Senate once again. A look at the RCP House and Senate rankings shows the odds heavily against the GOP this election.

Republican-held Senate seats make up 12 of the 14 on our most-vulnerable list, including the top 11. Of the top four seats most likely to change party hands, three are open seats due to an incumbent retiring -- the fourth is Alaska Sen. Ted Stevens, who is currently in federal court facing corruption charges. You will also find Senate Minority Leader Mitch McConnell in the top 10.

In our updated House rankings, Republicans make up seven of the top 10 and 15 of the top 20 most vulnerable races. Recent polling has shown that the economic crisis is moving potential votes toward Democrats. Check out our House ratings page to see which direction the top 50 races currently lean.

The presidential level is no different. Barack Obama surpassed 270 electoral votes on the RCP Electoral Map yesterday, boosted by Virginia's move from a toss-up state to leaning in Obama's favor.