Newly re-elected President Barack Obama will once again deal with a divided Congress as Democrats retained control of the US Senate, while Republicans kept their solid majority in the House of Representatives.
But two Republican candidates in Missouri and Indiana who had made damaging comments about rape and abortion were both defeated and an incumbent Republican fell in liberal Massachusetts. Republicans also lost a seat in Maine, where an independent who is expected to vote with the Democrats won, while picking up a Democratic-held seat in Nebraska.
More than two billion dollars was spent on the fight for Congress. All 435 House seats were on the ballot, and Republicans retained control there, though Democrats made a few gains. That means Mr Obama will have difficulty passing any ambitious legislation in his second term.
Only a dozen or so Senate races out of the 33 on the ballot were seen as competitive, and almost all of those that were called yesterday - in Wisconsin, Virginia, Connecticut, Missouri, Ohio, Pennsylvania, New Mexico and Florida - went the Democrats' way. That left them poised to retain or even increase their 53-47 advantage in the Senate.
Control of the Senate at the very least gives Democrats a firewall against Republican attempts to overturn Obama's signature legislative achievement, his health care reform law, before it is fully implemented in 2014. Republicans had promised to repeal it.
Democrats began the year in a precarious position, defending 23 Senate seats and losing several retiring veterans in Republican-leaning states, all while voter discontent lingered over the sluggish economy and Mr Obama's health care law.
Congress consistently rates low in public opinion surveys, but incumbents still tend to get re-elected. They benefit from a system that gives them huge financial advantages in their re-election bids, and enjoy support from voters who tend to favour their own politicians even if they dislike Congress overall. Many incumbents in the House were also helped by the once-a-decade redrawing of district boundaries, which has just been completed.
In Missouri, another state won by Mr Romney, Senator Claire McCaskill had been considered the most vulnerable Democratic incumbent, but she defeated another tea party-backed candidate, congressman Todd Akin, who won the Republican primary.
Mr Akin was disowned by Republican leaders, including Mr Romney, after he remarked in August that women's bodies have ways of avoiding pregnancy in cases of what he called "legitimate rape".