President Obama won a second White House term Tuesday night, overcoming concerns about the fragile economic recovery to soundly defeat Republican nominee Mitt Romney.

"We've got more work to do," Obama declared, addressing a cheering crowd at his victory rally in Chicago early Wednesday morning. Obama spoke to supporters at his campaign headquarters shortly after Romney called the president to concede. Obama congratulated his opponent on a "hard-fought campaign."

After one of the nastiest political battles and most gridlocked terms in modern American history, the president vowed to reach out to the other side in a second term on everything from immigration to the deficit. He asked supporters to keep the "hope" and said that while the "passions" and "controversy" won't wane after Election Day, "progress will come in fits and starts."

"While our journey has been long, we have picked ourselves up, we have fought our way back and we know in our hearts that for the United States of America, the best is yet to come," the clearly fired-up president told the crowd.

Romney conceded shortly after midnight, delivering a brief speech to a subdued crowd of supporters at his Boston headquarters, where he said he would "pray that the president will be successful in guiding our nation."

The former Massachusetts governor urged Washington's politicians to set aside the "bickering" and "political posturing" going forward, and "put the people before the politics."

"This election is over, but our principles endure," Romney said.

The president's projected victory came shortly after he was declared the winner in the crucial battleground of Ohio. The president was leading by a narrow margin in that state as returns continued to stream in overnight, but a streak of victories in other battlegrounds put him well over the 270 electoral votes required to win. The count, with the results from Florida still not in, stood at 303 electoral votes for Obama, to Romney's 206.

Obama held a narrower lead in the popular vote count. But despite that and the race being tied up nationally in polls leading up to the election, Obama's investment -- in time and money -- in a handful of swing states evidently paid dividends. Obama scored a big win in Pennsylvania, a vital contest where Romney made a late play for support. Obama also walked away with wins in the swing states of Virginia, Colorado, Iowa, Nevada, New Hampshire, Wisconsin and Michigan.

The victory caps a campaign that was far tougher in its tone than the president's 2008 run. On defense over a term marked by lackluster economic growth, Obama sought to cast Romney -- even before he was nominated -- as an elite, tax-dodging, corporate champion. His campaign seized on hidden-camera comments in which Romney said 47 percent of Americans, those who don't pay federal income taxes, consider themselves "victims."

He and Democratic officials also hammered the message that Romney's policies would be bad for women, in an appeal to an important voting bloc for the president who in exit polls backed Obama, 55-43 percent.

Romney, though, accused the man who ran in 2008 on big ideas of going small because he couldn't defend his first-term record. The Republican nominee, who emerged bruised but not broken from a protracted primary battle, initially struggled to gain on Obama in the polls. But following a strong lead-off debate performance in October, Romney drew the race to what appeared to be a dead heat.

Romney was able to capture a key victory Tuesday night in the battleground of North Carolina, a state Obama won in 2008 and where Democrats held their 2012 convention.

Elsewhere, Obama and Romney each racked up expected victories Tuesday night in relatively safe territory.

Romney was the projected winner in Utah, Montana, Alaska, Arizona, Missouri, Idaho, Texas, Louisiana, Kansas, North Dakota, South Dakota, Nebraska, Wyoming, Alabama, Mississippi, Oklahoma, Tennessee, Arkansas, West Virginia, South Carolina, Georgia, Indiana and Kentucky.

Fox News projected Obama the winner in home state Illinois, Oregon, California, Hawaii, Washington, Minnesota, New Mexico, Maine, New York, Delaware, Connecticut, Maryland, Massachusetts, New Jersey, Rhode Island, Vermont and the District of Columbia.

Election Day was unexpectedly busy for the campaigns. While Obama himself kept a low profile in Chicago, the campaign dispatched Vice President Biden to Ohio where he visited a Cleveland restaurant and later posed for pictures with volunteers before joining up with the president.

Romney, meanwhile, made stops in Ohio and Pennsylvania before heading back to campaign headquarters in Boston.

The presidential election coincided with hundreds of congressional races, as well as a slew of votes on controversial state ballot initiatives across the country.

As races continued to be called well into the morning, it appeared that the balance of power in Washington would remain the same next year. Republicans kept their majority in the House, while Democrats fended off a series of challenges to retain their majority in the Senate.

The vote Tuesday marked the end of a grueling and costly election cycle. Aside from all the money spent and raised in the congressional races, each of the presidential candidates raised roughly $1 billion. For Obama, the election was the last time he said his name will appear on a ballot. For Romney, the election closed out a nearly six-year run for the presidency. The Republican nominee ran unsuccessfully for the nomination in 2008.

The 2012 campaign was decidedly different from 2008, when Obama ran on a lofty message of change and leveraged voter dissatisfaction with the George W. Bush administration -- particularly the war in Iraq -- to defeat Republican nominee John McCain.

This time around, each candidate's campaign message was bound to the state of the economy, having gone through a recession shortly before Obama took office. Romney argued forcefully that Obama failed to deliver the kind of economic rebound that typically follows a downturn.

The Republican nominee accused the president of throwing money at the problem with a poorly designed stimulus and then abandoning the issue altogether to focus on passing ObamaCare. Romney argued that the health care law, along with countless regulations and an allegedly anti-business attitude, all combined to stand in the way of a full-throated recovery. Issues like the Libya terror attack and the threat from Iran's nuclear program brought foreign policy into the mix, but the economy remained central.

Yet Obama argued all along that, despite the slack in the system, the country was moving in the right direction. He pointed to recent economic reports, including Labor Department data showing the jobless rate falling below 8 percent for the first time since he took office, as signs that the economy was improving and would get better over time.

He warned that Romney's agenda -- which he described as tax breaks for the rich and giveaways to corporations -- would only reprise the "failed" economic policies of the prior administration, which he claimed led to the recession.