WASHINGTON — In President Obama's first term, a promise of bipartisanship withered on stony ground; as his second begins, he has openly embraced confrontation.

On a parade of hot-button political issues, including the budget, gun control and immigration, Obama has begun to hammer on weak points in the Republican coalition.

He has made little effort to woo members of the opposition inCongress, whose positions he has characterized publicly as "intransigent," "extreme" and "absurd." Instead, he appears intent on dividing them.

That approach has unified Democrats, who remain staunchly supportive of the president, while exacerbating splits in Republican ranks, according to polls. While the strategy involves considerable risk, Obama and his aides seem convinced it offers their best hope of winning major legislative victories in an era of deep partisan divisions in Washington and in the wider electorate.

The administration wants to "stay away from inside-the-Beltway, elite negotiations and try to pursue an outside-in strategy, where the president seeks to mobilize public opinion and put pressure on a minority of Republicans," said William Galston of the Brookings Institution, a public policy think tank.

The idea, he said, is to find weak spots in the GOP coalition, then "stick a wedge into the crack and wiggle it back and forth until it breaks."

During the first term, Obama and his aides engaged in lengthy negotiations and offered concessions aimed at winning a handful of Republican votes during battles over healthcare and the economic stimulus.

That effort proved futile, whether because of Obama's inability to reach across the aisle (the Republican view), the intransigence of his opposition (the Democratic version) or the inherent problems of compromise in a divided country.

During the presidential campaign, Obama and top aides suggested that the Republican determination to oppose him would wane if he won reelection. "The fever will break," became a favored White House metaphor.

That hasn't happened, and the current White House strategy tacitly acknowledges that bridging the partisan gaps will probably remain beyond Obama's power. At the same time, Obama and his advisors feel more confident they can prevail — as they did during the "fiscal cliff" battle over tax rates in December.

White House senior advisor Valerie Jarrett said Obama was not adopting "a confrontational strategy," but was acting confidently "with the experience of four years."

"His intent isn't to cause fracases in the Republican party," she added, saying that the focus is on policy. "The way he looks at it is, these are causes that can actually bring our country together."

Republicans disagree, of course, and say Obama's approach guarantees nothing will get done.

"The president is really good at campaigning and really bad at governing," said Republican strategistWhit Ayres. "Anything that's going to get through this Congress is going to have to be done in a bipartisan way," he said, but Obama has shown "no inclination or ability" to accomplish that.

"This White House hasn't seemed to have figured out that the election is over, and the time for governing has come," he added.

Whichever view is right, the legislative clock runs quickly for second-term presidents.

Next year, members of Congress will begin to focus on the 2014 midterm election. After that, the 2016 presidential contest will rapidly take shape. Even if he avoids the kinds of scandals or blunders that hindered the second terms of Dwight Eisenhower, Richard Nixon, Ronald Reagan, Bill Clintonand George W. Bush, history suggests Obama has a relatively short period in which to collect legislative victories.

"In second terms the window of opportunity is pretty narrow, maybe 18 months," said University of Texas professor H.W. Brands, one of a group of historians who have met several times with Obama for off-the-record dinners to discuss the presidency. "After that, they are really lame ducks."

Obama and his aides dismiss the idea that a softer approach to the opposing party would lead to a better result.

Members of Congress chiefly vote based on their political self-interest, not personal relationships, Obama said at a recent news conference. "The reason that, you know, in many cases, Congress votes the way they do, or talks the way they talk, or takes positions and negotiations that they take — it doesn't have to do with me; it has to do with the imperatives that they feel in terms of their own politics," he said.

Many outside experts agree. The biggest fear for many lawmakers is the risk of being challenged in a primary election if they cooperate with the other side, said Alan Abramowitz, professor of political science at Emory University, who has extensively studied the country's rising political partisanship.

The gap between the two parties in the just-completed 112th Congress was bigger than at any time since the 1880s, according to data analyzed by University of Georgia political scientist Keith T. Poole. To convince members to break party discipline in such a divided body, the president has to provide significant counter-pressure.

White House aides "see that they have the advantage" with public opinion on guns, taxes and other major issues Obama has tackled, Abramowitz said, and "that plays into this more confrontational approach."

White House officials believe events have vindicated their strategy. In December's confrontation over the federal budget, Obama made an initial offer that embodied an extensive Democratic wish list. House Republicans denounced him for not negotiating seriously, vowed to block his plans to raise income tax rates on the wealthiest Americans, then gave in when the deadline arrived.

Obama made some concessions, but far fewer than in previous negotiations. In the end, SpeakerJohn A. Boehner (R-Ohio) allowed a tax increase on the wealthy to come to the House floor and pass despite opposition from most of his caucus. The bill marked the first time any Republican in Congress had voted for an income tax hike in more than 20 years.

Republican leaders then vowed to recoup their losses in a fight over the federal debt ceiling. On Friday, they backed away from that confrontation too, judging the risks too high, and proposed a new budget deadline later in the spring.

Obama and his aides hope the budget vote established a template for other votes coming to the House floor without support from a majority of Republicans.

On immigration, Obama plans to offer a proposal that would create a path to citizenship for most of the country's estimated 11 million illegal residents. The measure would go much further than immigration efforts that failed even to come to a vote in his first term. What may make passage possible, advocates argue, are Republican worries about the party's disastrous showing among Latino voters in the November election.

Mitt Romney received only 27% of the Latino vote, burying his presidential hopes in several battleground states. Many Republican strategists insist the party needs to make concessions on immigration to win future elections.

A tougher test will come on gun control. White House strategists hope public outrage over the school massacre in Newtown, Conn., will push members of Congress in relatively moderate, suburban districts away from the National Rifle Assn. and its allies. Dividing the GOP would provide cover for Democrats from conservative states who are the keys to winning passage of any gun measures in the Senate.

If all that works, the administration could significantly toughen the nation's system of background checks for gun purchases. That's a change Democrats have sought unsuccessfully since the mid-1990s. If public pressure mounts high enough, they hope to win other new laws, including a ban on high-capacity ammunition magazines.

On both issues, the potential benefits for Obama outweigh the risk of stalemate, said Ruy Teixeira of the Center for American Progress, a Democratic think tank with close ties to the administration.

If Republican opposition cracks, the president can win major victories. If the Republicans vote down his proposals, "the Republicans are now the party that's viewed as being fundamentally intransigent," and the votes could help Democratic candidates in future elections, he said.

Either way, he said, White House officials believe "it's going to be a net benefit to them."