Obama, elected on a heady wave of hope and change in 2008, compiled a historic resume of domestic legislative triumphs, overhauling health care and Wall Street and pumping billions of dollars into the crisis-strangled economy.
He succeeded by uniting his Democratic Party and adding several moderate Republicans to pass bills over the objection of their leaders. But such tactics will become obsolete in the new Washington that emerges after November 2 polls.
Even if Republicans do not pull off a seizure of the House of Representatives and trim the Democratic edge in the Senate, as most analysts expect, Obama is sure to see his room for maneuver curtailed.
History, and the dynamics of power in Washington, suggest Obama's political capital will be depleted after a mid-term rebuke from voters, with a testing run-up to his 2012 reelection bid in prospect.
"One way or another, next week's elections are going to deliver a humbling blow to the Democrats," said Costas Panagopoulos, editor of "Campaigns and Elections" magazine.
"If they refuse to be humbled, they will pay a price at future elections," added Panagopoulos, a Fordham University professor.
Polls predict a Republican House that would thwart Obama on major legislation. Even if Democrats cling on, their wafer-thin majority would leave the balance of power with conservative members of their caucus.
A more evenly divided Senate meanwhile portends gridlock.
Obama appears to have two choices.
He could confront Republicans and pin them with the blame for an era of political conflict at the next presidential election in 2012.
Or, the president could coax Republicans toward areas of compromise and mutual interest -- though any resulting legislation is likely to be far less consequential than his earlier triumphs.
During the 2008 campaign, Obama raised eyebrows when he said that unlike former Democratic president Bill Clinton, Republican Ronald Reagan had changed the "trajectory" of American politics.
But many observers now feel Obama must borrow the playbook of compromise, domination of the center ground and savvy positioning that landed Clinton a second term after his party was hammered in 1994 mid-term polls.
"Is Obama willing to settle for a number of small, incremental measures that add up to something successful?" asked University of Arkansas professor Andrew Dowdle, voicing a key question of the next two years.
Some analysts say that education, deficit reduction, stalled foreign free trade deals and energy reform offer prospects for compromise if both parties feel an obligation to show voters they can work together.
But efforts on global warming and comprehensive immigration reform appear to be out -- unless Obama can launch a new era of reform with a second term mandate after 2012.
In theory, Obama should be well placed: he made his name in a breakout 2004 speech preaching that there was no red (Republican) America or blue (Democratic) America.
"Barack Obama issued a promissory note to the American people which he has yet to redeem, namely to make a country divided into red and blue Americas into one America," said William Galston of the Brookings Institution.
However, Obama's lofty promises to drain the poison of Washington politics fell short.
Should Obama chose cooperation, it is uncertain whether his Republican foes will have the inclination -- or the political capacity -- to help.
An influx of ideological conservatives from the Tea Party movement may push the party's leadership further to the right, narrowing room for compromise.
And with a looming general election, Republicans have little incentive to bolster a Democratic president.
Republican Senate leader Mitch McConnell signaled that Republicans may be flexible, but only strictly in their own interests.
"Our single biggest political goal is to give our nominee for president the maximum opportunity to be successful," he told National Journal.
"We need to work smarter than we did (after 1994), and not become the foil off which (President Obama) pivots."
There are also questions about the political dexterity of the Obama White House, which mastered campaigning but has proved less flexible in government.
Obama has often seemed to disdain the kind of presidential politicking needed in a divided Washington.
Sometimes seen as aloof, he lacks the backslapping charisma of Bill Clinton, the mastery of congressional powerbroking of Lyndon Johnson or the disarming charm of Ronald Reagan.
Source: AFP American Edition