In Missouri, Rep. Todd Akin won the GOP nomination and days later made a comment about “legitimate rape” rarely causing pregnancy that created a national firestorm. Much of the party establishment abandoned Akin, but he refused to drop out of the race. Sen. Claire McCaskill (D) is favored to win reelection.
Democrats have growing confidence that former Obama administration official Elizabeth Warren, a Harvard law professor, will beat Sen. Scott Brown (R) in Massachusetts. The contest is the premier Senate race in the country for the seat long held by the late Edward M. Kennedy (D).
Explore the 2012 electoral map and view historical results and demographics
The Washington Post’s Scott Clement runs through the numbers of the Post-ABC News daily tracking poll. Obama had an advantage in early voting over John McCain in 2008, but that might not be the case in 2012.
Republicans have a number of opportunities to pick up seats held by retiring Democrats. Races in Nebraska and North Dakota, where Democrats are retiring, seem likely to fall for Republicans. Virginia has a very tight race between two former governors: Democrat Timothy M. Kaine and Republican George Allen. In Montana, Sen. Jon Tester (D) and Rep. Denny Rehberg (R) have been tied for months.
Even if several of those races tip to Republicans in the final hours, it still seems unlikely that the GOP will add the four seats it would need to control the Senate if Obama is reelected or the three it would would need if Romney wins. The most likely outcome is no net change, or Republican gains of one or two seats.
In the battle for control of the House, it has become clear over the past few months that the wave of elections that roiled the chamber in 2006, 2008 and 2010 will not be repeated Tuesday. Democrats need 25 seats to regain the majority. Not even their most optimistic strategists think that is anything more than a remote possibility.
Because of the decennial redistricting process, both parties will score heavy gains in certain states. Republicans look poised to pick up at least three and maybe four seats in North Carolina. Democrats could take five seats from Republicans in Illinois.
After taking control of more governorships and state legislatures in 2010, Republicans had the political muscle to carve up new congressional districts to their advantage. They shored up some of their most vulnerable incumbents and drew difficult districts for Democrats.
The result: Republicans are now likely to gain at least 10 Democratic seats simply because of the partisanship of redrawn districts, and Democrats are fighting from behind in their effort to win back the House. That is why overall Democratic gains may be held to the mid-single digits.
Aaron Blake, Sean Sullivan, Jon Cohen and Scott Clement contributed to this report.