His comment reflected the reality that many Republicans serving on Capitol Hill are not accustomed to the idea that the legislation they are pushing has a real chance of becoming law, because most of them had held office only while Barack Obama was in the White House.

“I think what you’re seeing is we’re going through the inevitable growing pains of being an opposition party to becoming a governing party,” the House speaker, Paul D. Ryan, said last week. “And in being an opposition party, we have divided government. Sixty-four percent of our members — 64 percent of our members — have never known what it’s like to work with a Republican president, to have unified government. So it’s a new feel.”

That is another way of saying that Republicans suddenly realize they are going to be held accountable for the impact the health legislation will have on their constituents, and it is making many of them very nervous. Up to this point, they have been able to put the blame on Mr. Obama. Now the blame, if there is any, will be directed at them. For many congressional Republicans, this is their first real attempt at enacting major social policy.

Despite obvious disagreements, Republican leaders and President Trump continue to put the best face on things and declare that their legislation is well on its way toward enactment. It is a tried-and-true strategy meant to create the impression that passage is inevitable and lawmakers would be wise to join the winning side. Nothing to see here.

“This is the time we’re going to get it done,” Mr. Trump said Friday at the start of a meeting with Republican congressional leaders. “We’re working together. We have some great results. We have tremendous spirit, and I think it’s something that’s just going to happen very shortly.”

On Thursday, Mr. Trump, quickly adapting to the Republican practice of keeping quiet any intraparty squabbling, said on Twitter that “despite what you hear in the press, health care is coming along great.”

Yet Republicans in the House and Senate say it is currently impossible to predict whether the health care legislation will pass, and warned that it was going to take substantial arm-twisting by Mr. Trump and congressional leaders, particularly given stiff opposition from aggressive interest groups with strong ties to House conservatives.