Mr. Obama has not been the sort to bludgeon his party into following his lead or to intimidate reluctant legislators. And while he has often succeeded by relying on Democratic leaders in Congress to do his bidding — the House and Senate, after all, both passed versions of the health legislation last year — it is not clear whether his gentle, consensus-building style will be enough.

“I wouldn’t mind seeing a little more toughness here or there,” said Representative Louise M. Slaughter, a New York Democrat, who contends that if Mr. Obama had pushed the Senate harder last year, the bill would have been law by now…

“If the president weren’t tough, if the president weren’t committed, if the president didn’t believe that this was an imperative for the future of American families, businesses and the sustainability of our budget, this thing would have been dead six months ago,” David Axelrod, Mr. Obama’s senior adviser, said in an interview. “I would love to live in a world where the president could snap his fingers or even twist arms and make change happen, but in this great democracy of ours, that’s not the way it is.”