Updated: 3:21 a.m.

Voters granted President Barack Obama another four-year term, capping the most expensive and divisive national campaign in memory and ensuring at least two more years of divided government in Washington, D.C.

Obama declared victory in a 22-minute speech in Chicago, thanking his supporters as well as those of Republican nominee Mitt Romney.

“We are an American family and we rise and fall together as one nation and one people,” he said, predicting that despite the nation’s challenges, “the best is yet to come.” Obama made a bipartisan appeal, graciously thanking Romney and his family for choosing public service. “I look forward to sitting down with Gov. Romney to talk about where we can work together to move this country forward.”

The network and Associated Press calls that Obama would defeat Romney led to deafening chants of “Four more years! Four more years!” at Democratic election headquarters in Washington earlier in the night.

Romney conceded the election in a brief speech at 12:55 a.m., offering his congratulations to Obama. “I pray that the president will be successful in guiding our nation,” Romney said in Boston. The clearly pained candidate thanked his family and his supporters and called on the nation to come together. “The nation as you know is at a critical point. … Our leaders have to reach across the aisle to do the people’s work.”

Obama’s win — built on key swing states including Ohio, Nevada, Wisconsin, Iowa and New Hampshire, will give him a second term in a deeply divided nation, and he will be facing a similar lineup in Congress, which has thwarted the bulk of his agenda for the past two years. In his victory speech, Obama said he looks forward to working with leaders of both parties on dealing with the deficit, immigration, tax reform and getting off of foreign oil.

“We’ve got more work to do … but that doesn’t mean your work is done,” he said. “Our economy is recovering. A decade of war is ending. A long campaign is now over. And whether I earned your vote or not, I have listened to you. I have learned from you. And you’ve made me a better president.”

On Capitol Hill, Senate Minority Leader Mitch McConnell (R-Ky.) issued a sharp statement demanding that the president move in the GOP’s direction.

“Now it’s time for the president to propose solutions that actually have a chance of passing the Republican-controlled House of Representatives and a closely-divided Senate, step up to the plate on the challenges of the moment, and deliver in a way that he did not in his first four years in office,” he said in a statement given to the Louisville Courier-Journal. “To the extent he wants to move to the political center, which is where the work gets done in a divided government, we’ll be there to meet him half way.”

Obama’s victory came from a diverse coalition of women, minorities and younger voters while Romney racked up big margins among whites.

And already, Republican analysts were pointing to the steadily growing percentage of minority voters as a sign that the GOP needed to change its approach.

But Obama will still have to deal with Speaker John Boehner (R-Ohio), who will retain the gavel next year. Democrats fell well short of their quest to net the 25 seats needed to take back the House, which has been a killing ground for the president’s agenda for the past two years.

Boehner laid down an early marker in his victory speech at GOP headquarters against Obama’s repeated effort to raise tax rates on the wealthy back to the 39.6 percent rate they paid under President Bill Clinton. That’s been a staple of the president’s re-election campaign, which he based on restoring fairness to a middle class that has seen its incomes squeezed.

“With this vote, the American people have also made clear that there is no mandate for raising tax rates,” Boehner said. The statement appeared to leave open room for raising revenue in other ways, such as closing tax loopholes or limiting deductions.

Obama has previously said he would veto any extension of those tax breaks for the wealthy — the chief issue at stake as Congress tries to defuse a fiscal bomb of its own making by the end of the year.

Nor was there much of an olive branch toward enacting the rest of Obama’s agenda.

Still, Obama will have allies again in the Senate, where Sen. Harry Reid (D-Nev.) will remain Majority Leader after Democrats nearly swept the close races after a series of Republican missteps.

The combined Democratic victories solidify Obama’s legacy and assure that the GOP’s “repeal” agenda — including Obamacare and Dodd-Frank — is toast. And Republicans now face its own soul-searching between a still dominant conservative wing and more mainstream Republicans looking to move their party back to the center.

The win that put the president over the top was the critical state of Ohio — the focus of both candidates for months — and where Romney, his running mate Rep. Paul Ryan (R-Wis.) and Vice President Joseph Biden all made appearances on Election Day.

Exit polls showed that Obama’s rescue of General Motors and Chrysler helped him win the bellwether state. According to Fox News, exit polling showed Obama winning backers of the bailout, which was popular in the state, 75 percent to 23 percent.

And while many voters remained unhappy with the economy, many still blame Obama’s predecessor, George W. Bush, more than the president.

Obama held on to Wisconsin, Ryan’s home state, despite Ryan and the Romney campaign devoting enormous time and resources. He also won the key states of Colorado and Virginia, which were heavily targeted by both sides.

At Republican and Democratic election night events in Washington, D.C., it was clear Democrats had the better time.

With Obama racking up wins in battleground states and Romney struggling to put one away, the GOP party at the Ronald Reagan Building and International Trade Center seemed to be thinning out after 10 p.m. At one point, a smattering of applause rang through the hall when Fox News announced Romney had won Utah.

Attendees seemed to be clinging to any good news after announcements that Democrats won Senate seats in Massachusetts and Indiana. But they soldiered on for a while, holding out hope despite the fact that it was a cash bar.

At the packed bar outside the main ballroom at the Liaison Capitol Hill hotel, eager Democrats crowded around televisions and burst into cheers as CNN called Pennsylvania for the president and the Massachusetts Senate race for Elizabeth Warren within moments of each other. Staffers and donors milled anxiously about the main party space, waiting for enough Senate races to be called to be able declare themselves the majority-holders yet again.

They would not be disappointed.

Humberto Sanchez, Meredith Shiner and Emma Dumain contributed to this report.