Sitting President Barack Obama won. As Robert Barnes reports:

A sharply divided America awarded President Barack Obama a second term Tuesday, choosing him over Republican Mitt Romney to lead the repair of an economy that by far remains the country’s biggest concern, the Washington Post projects.

The president was poised to narrowly win several tight races in a handful of battleground states. It was the culmination of a staggeringly expensive, extremely close and sometimes bitter contest far removed from Obama’s 2008 message of hope and change.

Democrats also held onto their majority in the Senate, picking up two seats in early returns with the possibility of a third.

By 11 p.m., Obama had already won the battleground states of Pennsylvania, Iowa and Wisconsin, the home of Romney’s running mate Rep. Paul Ryan.

Yet as Dan Balz reports, Obama now faces the challenge of building a new landscape:

The irony is that the most expensive election in American history produced a status-quo outcome. Now the question is whether it will change the status quo that has governed Washington not just during Obama’s presidency but for most of the past decade.

Obama will confront a daunting agenda, from an economy that is still far less robust than he had promised it would be to the looming problem of debt, deficits and the growth of federal entitlement programs that produced an ugly battle during his first term. The “fiscal cliff” looms in December, which either will force action and agreement or define a new landscape of disagreement.

Tuesday’s election produced an uncertain mandate, although Obama will attempt to claim one. Obama offered a plan for the future, but not one that deals directly with some of the problems he will have to confront immediately. His campaign was geared more to defining and attacking opponent Mitt Romney than creating a mandate for a second term.

Ezra Klein takes a look at Obama’s second term as well, focusing on the opportunity the president has to bring about changes he set in motion during the first four years:

They say that presidents campaign in poetry and govern in prose. That’s rarely been truer for a president than it was for Obama, whose inspiring oratory launched him to the White House and whose grind-it-out, insider-game approach to working with Congress disappointed his fans. But it worked. That prose became law — but, unusually, it became law that wouldn’t fully take effect until his second term. So while in 2008, his election was a vote for hope, in 2012, his reelection carries a guarantee of change.

Chris Cillizza, meanwhile, examines the biggest political lessons to be learned from Obama’s reelection, including:

This wasn’t JUST an economic referendum: Former Massachusetts governor Mitt Romney built his entire campaign around the idea that the only question for voters was “Are you better off than you were four years ago?”  The goal was to turn the entire election into a straight referendum on President Obama’s handling of the still struggling economy.  It didn’t work. Almost six in ten voters said the economy was the the top issue for them and among that group Romney won 51 percent of the vote 47 percent for President Obama.  And yet Romney lost — and lost convincingly.  Why? Obama turned the race effectively into a choice between someone who voters thought understood them and their concerns and someone who didn’t.  One in five voters said that a candidate who “cares about people like me” was a critical piece of their decision; Obama won them 82 percent to 17 percent.