WASHINGTON — Democrats retained their majority in the U.S. Senate on Tuesday, an outcome that leaves a divided Congress that closely resembles the one that has been gridlocked for the past two years on some of the nation's most pressing issues.
A combination of misfortune and mistakes left Republicans unable to seize control for the second straight election in which they were early favorites to make historic gains.
In a key race between Virginia political heavyweights, former Gov. Tim Kaine, D, defeated former Sen. George Allen, R.
Kaine's victory ended an attempt at political redemption by Allen, a one-time presidential contender who was unseated in 2006 by Sen. James Webb , D.
The Democrats flipped Republican Senate seats as the GOP saw sure-bet Indiana slip away. Democrat Rep. Joe Donnelly defeated conservative state treasurer Richard Mourdock, who sank after saying that he believed that pregnancies that result from rape reflected the will of God.
In Massachusetts, liberal hero Elizabeth Warren gave Democrats an emotional win by snatching back the seat once held by Sen. Edward Kennedy, D, from Republican Scott Brown.
After a series of hard-fought and sometimes nasty battles in Senate races that spanned the country, little changed in the chamber: Democrats were likely to expand on their current 53-to-47-seat edge.
But neither party appeared to be in a position to gain the seats necessary to win a filibuster-proof 60-seat majority, meaning a continuation of the gridlock that has been a hallmark of the modern Senate.
Still, a bare majority for Democrats offers them the chance to control the chamber's agenda and committee structure. With that edge comes new leverage in negotiations over the nation's most difficult problems, including fiscal issues that must be addressed even before the next Senate takes office.
With the GOP retaining control of the U.S. House of Representatives, Democrats needed to hold the Senate as a legislative ally to a reelected President Barack Obama.
Until recently, Democrats were thought to be in danger of losing the Senate, given that only 10 Republican seats were up for grab this year, while 23 Democratic seats were in play, including in a number of Republican-leaning states.
The GOP missteps of the 2012 race are likely to lead to a party reckoning before 2014, when Democrats will once again be defending more seats than Republicans.
Republican troubles began when moderate Sen. Olympia Snowe, R, announced her retirement, citing the Senate's bitter partisanship, paving the way the loss of a GOP seat to independent former Maine governor Angus King.
Then establishment Republicans lost control of state nominating contests, as they did in 2010, and watched as the fate of the Senate was handed to candidates ill-suited to general elections.
Two Republicans who won their party's nomination with an appeal to the party's right uttered cringe-worthy statements about abortion and rape, putting likely GOP wins in doubt.
In Missouri, Rep. Todd Akin, R, was abandoned by national Republicans, including Mitt Romney, after saying that pregnancies rarely result from from "legitimate rape."
He apologized but was haunted by the remark and lost Tuesday to Democratic Sen. Claire McCaskill, who was once thought to be one of the nation's most endangered incumbents.
The Democratic win in Indiana was especially painful to Republicans because Mourdock got on the ballot only after defeating 36-year incumbent Sen. Dick Lugar, R, in a bitter primary battle.
Republicans were also plagued with difficulties recruiting top-notch candidates, leaving lesser-known or flawed nominees battling in some of the nation's biggest and most important electoral contests.
In Florida, Democratic Sen. Bill Nelson defeated Rep. Connie Mack, even as Romney and Obama were locked in a tight race late in the evening in the state.
The same was true in all-important Ohio, where Sen. Sherrod Brown, D, defeated state treasurer Josh Mandel.
Some of the nation's marquee races were centered in states where the presidential election was not in doubt.
They included Massachusetts, home to perhaps the country's most closely watched Senate campaign. There, Brown campaigned as an independent-minded everyman against consumer crusader Warren, who argued that Obama needed a Democratic ally in the Senate.
The contest held deep emotional resonance for both sides. Democrats longed to regain a seat that had been lost in a special election after Kennedy's death in a race that was dominated by the national debate over health care reform.
In Connecticut, former wrestling executive Linda McMahon, R, also ran as an independent voice, but lost to Rep. Chris Murphy despite spending millions of her own money to convince voters supporting Obama that they could also vote for her.
Romney was expected to easily win the presidential race in Montana and North Dakota — but the deeply conservative states were home to two of the nation's most hotly contested Senate races.
In Montana, Sen. Jon Tester, D, faced Rep. Denny Rehberg. And in North Dakota, Rep. Rick Berg, R, faced a surprisingly tough battle from former state attorney general Heidi Heitkamp to replace Sen. Kent Conrad, D, who will retire in January.
And Republicans were ahead in one state now held by Democrats — Nebraska. In that race, state Sen. Deb Fischer, R, led former Senator Bob Kerrey, D, in early returns in a race to replace retiring Sen. Ben Nelson, D.
But the presidential battlegrounds also saw tight races, including Wisconsin, where former Republican governor Tommy Thompson, R, was locked in a tight race with Rep. Tammy Baldwin, who would be the nation's first openly gay senator if elected.
In Pennsylvania, Sen. Robert Casey, D, who had long been thought likely to sweep to easy reelection, defeated coal executive Tom Smith, who spent more than $17 million of his own money on the race.
And in Nevada, Sen. Dean Heller sought to win reelection against Rep. Shelley Berkley, even as she tied herself to Obama and leaned heavily on a turnout machine headed by Senate Majority Leader Harry Reid.