“There’s absolutely no path to move forward on a bipartisan basis with Mitt Romney,” Van Hollen said, noting that bipartisan commissions have recommended both spending cuts and tax increases. “He himself has taken the bipartisan solution off the table.”

Van Hollen said that if Obama is reelected, he would be able to convince enough Republicans that the public wants a compromise approach.

Republicans, however, have argued that it was Obama and the Democrats who set the course for polarization by passing the 2009 stimulus package and the 2010 health care legislation despite overwhelming Republican opposition.

“Give me a break,” said Representative Jason Chaffetz, a Utah Republican and Romney adviser. Obama “didn’t fulfill the promise of bridging the partisan divide. When he said that ‘we are not red states, we are not blue states, we are the United States,’ everybody cheered that line. The problem is it didn’t happen.”

The partisan furies in Washington did not suddenly rise in a vacuum. Much of the rancor between the parties sprang from the tumultuous geopolitical and economic events of the past decade. George W. Bush’s first-term invasion of Iraq and the prolonged war proved deeply unpopular, stirring a wave of anger among liberal Democrats. Antiwar sentiment, combined with upheaval and dismay during the economic crisis of 2008, helped sweep Obama into office.

But Obama’s mandate quickly eroded. Strong Republican opposition to the new president’s economic and health care initiatives was manifested by growth of the Tea Party and the GOP takeover of the House in 2010. For virtually all of Obama’s term, the parties engaged in intense ideological warfare about the appropriate role of government and the size of the social safety net.

Polling conducted by the nonpartisan Pew Research Center revealed the deepest ideological divide in 25 years between Americans who identify with one or the other of the two major parties. The size and performance of government, the future of the safety net, immigration policy, and environmental protection are the areas of deepest disagreement.

“Part of the antagonisms in Washington has to do with the fact that the country has become that way too,’’ said Andrew Kohut, president of the Pew Research Center.

The gaps are partly caused by geographic and demographic differences. Rural America has long favored Republicans, while the financial and education centers on the coasts vote Democratic. Those seemingly indelible red and blue patterns on the electoral map reveal why just only a half-dozen or so states — Ohio and the other swing states — play outsized roles in deciding presidential elections.

Specialists say recent economic anxieties have made these partisan differences more profound – conservatives want less spending while Democrats see greater need for government assistance to the disadvantaged.

Booming exurbs across the country, for instance, have been hit hardest by the mortgage industry collapse and foreclosure crisis. Residents of all those sprawling subdivisions are frustrated by dwindling employment opportunities and plunging home values — and they tend to identify themselves as Republican.

Higher government spending on the social safety net and big programs like “Obamacare” rankle residents of these far-flung exurbs more than their liberal, wealthier counterparts in traditional suburbs, said Dante Chinni, executive director of Patchwork Nation, a project of the nonprofit Jefferson Institute in Washington that closely tracks the political preferences of demographic and geographic groupings.

“It’s a lot easier to see it as wasteful, particularly when you’re struggling,’’ said Chinni.

Both sides in Washington couch their arguments in terms of fairness, but the visions of what is fair are fundamentally at odds. Democrats see the path out of gridlock as resting on creating a fairer playing field for the middle class, a better-regulated economy, and a more progressive tax system that ensures the wealthy pay their fair share. Republicans describe fair government as one that regulates less, levies fewer taxes on “job creators,’’ and spends less on providing economic security to the disadvantaged.