HONOLULU — President Obama is heading into his re-election campaign with plans to step up his offensive against an unpopular Congress, concluding that he cannot pass any major legislation in 2012 because of Republican hostility toward his agenda.

Mr. Obama’s election-year strategy is an attempt to capitalize on his recent victory on a short-term extension of the payroll tax cut and on his rising poll numbers. As the stage is set for November, he intends to hammer the theme of economic justice for ordinary Americans rather than continue his legislative battles with Congressional Republicans, said Joshua R. Earnest, the president’s deputy press secretary, previewing the White House’s strategy.

“In terms of the president’s relationship with Congress in 2012,” Mr. Earnest said at a briefing, “the president is no longer tied to Washington, D.C.” Winning a full-year extension of the cut in payroll taxes is the last “must-do” piece of legislation for the White House, he said.

However the White House chooses to frame Mr. Obama’s strategy, it amounts to a wholesale makeover of the young senator who won the presidency in 2008 by promising to change the culture of Washington, rise above the partisan fray and seek compromises.