Republicans have easily maintained their hold on the House, while missteps from Tea Party favorites helped Democrats retain a majority in the Senate.
That means the two chambers of Congress remain deeply divided, with prospects for agreement on such big-ticket items as deficits, tax rates and climate change unclear.
In the House, Speaker John Boehner, R-Ohio, gloried in his party's victory — and laid down a marker. Saying he stands "willing to work" with his partners, Boehner added, "with this vote, the American people have also made clear there's no mandate for raising tax rates."
For his part, Senate Majority Leader Harry Reid, D-Nev., said, "The strategy of obstruction, gridlock and delay was soundly rejected by the American people. Now, they are looking for solutions."
Political analysts such as NPR's Mara Liasson say control of the chambers of Congress may not have changed, but the deeply unpopular body can't stay stuck.
"I don't believe we can go back to the exact same kind of zero-sum gridlock that we've had," Liasson said. "These kinds of problems that are facing the Congress can only be solved with a compromise."
It was also a night for history, especially in the Senate, where Republican Ted Cruz became the first Latino senator in Texas. Democrat Tammy Baldwin will be the first openly gay member of the Senate after defeating former GOP Gov. Tommy Thompson in Wisconsin. And several other women will join Baldwin, including Democrats Elizabeth Warren of Massachusetts and Mazie Hirono of Hawaii and Republican Deb Fischer in Nevada.
Not so long ago, Republicans had been hoping to capitalize on favorable election math to pick up as few as three or four seats and take over the Senate, sealing their hold on Capitol Hill.
But Democrats turned back that effort with key victories Tuesday by Harvard professor Warren in Massachusetts, Rep. Joe Donnelly in Indiana, Rep. Chris Murphy in Connecticut and Baldwin in Wisconsin.
The party got an extra boost with a win from Missouri Sen. Claire McCaskill, once considered their most vulnerable incumbent, from former Democratic Gov. Tim Kaine in Virginia, and from popular former Maine Gov. Angus King, a political independent. In an NPR interview after his victory, King wouldn't commit to caucusing with Democrats — but many election watchers believe he will.
Several key Senate victories put the Democrats in a safe position. In Massachusetts, the first-time candidate Warren picked off moderate incumbent Scott Brown, to give Democrats a hold on a seat held for decades by Senate lion Edward Kennedy.
In Indiana's race to replace GOP Sen. Richard Lugar, moderate Democratic Rep. Donnelly defeated Tea Party favorite Richard Mourdock. And in Connecticut, Murphy turned back a multimillion-dollar challenge from wrestling impresario Linda McMahon.
In Virginia, former Democratic National Committee chairman Kaine ran on his close ties to President Obama, defeating his fellow former Gov. George Allen.
In Missouri and in Indiana, Democrats got a boost thanks to controversies from opponents with ties to the Tea Party.
McCaskill had been considered quite vulnerable, but Rep. Todd Akin's comments about the unlikelihood of pregnancy after a "legitimate rape" drew national condemnation. Republican leaders and even members of the Tea Party Express pleaded with Akin to withdraw from the race, but he refused. Akin went on to compare his opponent to a "dog," fetching high taxes and red tape and bringing them home to Missouri.
But some Republicans had a good night.
Rep. Jeff Flake of Arizona defeated former U.S. Surgeon General Richard Carmona, in a race to replace retiring Sen. Jon Kyl. Flake has been a staunch opponent of earmarks and wasteful spending in his House tenure. And Cruz, a former U.S. Supreme Court clerk, easily defeated Paul Sadler.
Democrats also held onto seats in Ohio, Delaware, Florida, New York, New Jersey, Maryland, Minnesota, Pennsylvania and Rhode Island.
The vote totals represent a missed opportunity for the GOP, which could have seized control of the chamber by picking up a magic number of only three seats if Mitt Romney won, or four seats if the president was re-elected.
But this year, that goal loomed just out of reach — thanks, in part, to missteps by candidates with close ties to the Tea Party who made controversial remarks about rape, abortion and religion.
"It comes down to candidate selection," political analyst Matthew Continetti told NPR. "The GOP is going to have to look hard" at the process, he said.
Texas Sen. John Cornyn, who led the GOP Senate push, said the loss in the White House and the Senate meant "we have a period of reflection and recalibration ahead for the Republican Party."
Squeakers We're Still Waiting For
Montana: Incumbent Democrat Jon Tester faces six-term House member Denny Rehberg, who is emphasizing his deep roots in the state, his experience as a small-business owner and his fiscal conservatism. Rehberg has a slight lead in the polls, but most analysts consider this race a tossup.
North Dakota: Republican Rep. Rick Berg has been holding on to a small lead against Democrat Heidi Heitkamp, a former state attorney general who is trying to display her independence from Obama and is unpopular in the state. Retiring Sen. Kent Conrad, a Democrat, decided not to run for a fifth term.
Nevada: Incumbent Republican Dean Heller and Democrat Shelley Berkley are locked in a tight race, awash with millions of dollars spent on negative TV ads. The candidates could hardly be more different. Heller is a Mormon and a social conservative from a rural part of the state. He was elevated to the Senate after his predecessor, Republican John Ensign, departed following a sex scandal. Berkley, a U.S. House member representing the populous Las Vegas area, put herself through school by working as a cocktail waitress and a Keno casino game runner. She has strong union support.
In the U.S. House, Democrats have no chance of picking up the 25 seats they need to take the reins — even though Congress is unpopular and unproductive. The election wave in 2010 that ushered in dozens of Tea Party Republicans is unlikely to recede.
"The success of Republicans in redrawing the district lines of some vulnerable members, especially freshmen, has made it a very heavy lift for Democrats to get into the majority," says Thomas Mann, a longtime political scholar at the Brookings Institution in Washington.
So Mann is looking at a more narrow issue on Election Day: "the fate of some of the most prominent Tea Party enthusiasts."
Many of those lawmakers have become household names. For instance, there's onetime GOP presidential contender Michele Bachmann of Minnesota. Bachmann barely scrapped by to hold on to her seat and grab a fourth term against challenger Jim Graves, a Democratic businessman in his first political campaign.
There's also Allen West, a Tea Party favorite in Florida, who is running in a new district this year after state GOP mapmakers initially put him in a more Democratic district. West, a retired Army officer and one of two black Republicans in the House, hit the headlines earlier this year after claiming at a town hall meeting that more than 78 House Democrats are "communist." Challenging West is Patrick Murphy, a Democrat and first-time candidate who worked for his family's construction company doing restoration work after the BP oil spill.
In Illinois, GOP incumbent Rep. Joe Walsh lost to Democrat Tammy Duckworth. Earlier this year, Walsh complained that Duckworth, an Iraq War veteran who lost both of her legs in a helicopter crash, was talking too much about her military heroics. Duckworth responded by releasing a list of Walsh's bombastic remarks, which she called his "greatest hits."
Moments For History
Congress is saying goodbye to several prominent members who are retiring, including Democrat Barney Frank of Massachusetts, the first openly gay member of Congress; also leaving are Democrat Dennis Kucinich of Ohio and Republican Ron Paul of Texas, who have both run for president.
NPR's Rudin notes that the House races present any number of opportunities for "firsts." In New Hampshire, Democrats Carol Shea-Porter and Ann McLane Kuster have defeated their GOP male incumbents. Now, the state's entire congressional delegation, including its two senators, will be composed of women.
And in Massachusetts, there could be another moment ripe with history. Democrat Joe Kennedy III is running to fill the House seat long occupied by the retiring Frank. If Kennedy defeats businessman and Marine Corps reservist Sean Bielat, it would mark the return to Congress of the storied Kennedy family after the death of Sen. Edward Kennedy in 2009 and the departure of his son, Patrick, from the House in 2010.
Finally, in Utah, Republican Mia Love, who is black and Mormon, has been groomed for big things by GOP leaders and got a prominent slot at the national convention this year. She lost to incumbent Democratic Rep. Jim Matheson.
On The Radar
Three House incumbents up for re-election are on the radar of federal law enforcement. Republican David Rivera of Florida, Republican Michael Grimm of New York and Democrat Jesse Jackson Jr. of Illinois are all staring down FBI investigations of their spending or donor relationships. Jackson has won his re-election bid easily, and Grimm has prevailed as well, but Rivera fell to Joe Garcia.