Republicans in the House of Representatives were expected to vote on Wednesday to authorize a lawsuit against the president for exceeding his presidential authority while implementing the Affordable Care Act, his signature health care law.
The president, in a speech, made fun of his political adversaries, laughing as he accused them of wasting time instead of addressing more pressing issues.
"Stop being mad all the time. Stop - stop - stop just hatin' all the time," he said of Republicans, drawing loud cheers from a raucous crowd of about 1,500 in an ornate theater in Kansas City.
While the lawsuit would focus on the health law, Republicans have complained that Obama's use of executive actions to take other steps, such as raising the minimum wage for federal workers, risks giving him "king-like authority."
Obama disparaged the expected lawsuit as nothing but election-year political theater and a distraction from issues such as highway construction or the southwestern border crisis.
"There's a bunch of stuff that needs to get done," he said. "Unfortunately, I think the main vote ... that they've scheduled for today is whether or not they decide to sue me for doing my job."
But an influential Republican, House Budget Committee Chairman and former vice presidential candidate Paul Ryan, backed the lawsuit, which he said is justified because it would protect Congress' powers under the U.S. Constitution.
"The lawsuit has intellectual merit because we want to show that we're not going to take this lying down," Ryan said at a breakfast hosted by the Christian Science Monitor. "The president is issuing executive orders and regulations that exceed the parameters of the statutes that give him the authorities in the first place."
With Republicans in control of the House, Obama's agenda has been thwarted by congressional gridlock, leaving him to take executive actions to make changes where he has the power to do so.
The president has been delivering variations of the fiery stump speech all summer as he tours the country trying to motivate Democrats - and wealthy donors - to get involved in November's congressional elections.
His aim is to energize Democratic voters ahead of the elections in hopes of stopping Republicans from gaining control of the Senate, which, if joined with a Republican hold on the House, could make it extremely difficult for him to pursue his agenda in his last two years in office.
Polls show Democrats will have a hard time holding control of the Senate in the midterm elections, while Republicans are expected to keep control of the House.
Republicans have criticized Obama for his road trips, saying his time would be better spent addressing a series of domestic and foreign crises.