Washington (CNN) If House Speaker Paul Ryan manages to finally muscle through the GOP health bill on Thursday, he will temper a damaging period of false starts, soul-searching and splits in his party that tarnished the start of Donald Trump's presidency.

Trump has struggled to assert his authority on Washington since taking office -- after telling his fired up and loyal voters he would do just that and change the way the gridlocked capital works. It became a cliché of the reviews of his first 100 days that the President was yet to celebrate a major legislative victory.

The White House has had to endure a barrage of criticism as the conservative majority has fiddled over Obamacare repeal. Often the President has seem ill-informed about actually what is in the evolving bill, in a way that has undercut his claims to be the ultimate dealmaker.

Some Republicans members were keen to talk up the President's role, even though some sources had previously described his frequent interventions as counterproductive.

"He's been all over this like a dog on a bone," Rep. Bill Flores of Texas said.

GOP Rep. Chris Collins told CNN he also credited Trump for the bill, saying, "This was Donald J. Trump the negotiator getting it done."

"What finally got this over the line was the President," he said.

In the House, Republicans will finally be able to go home to their districts for next week's recess and tell their frustrated base they have at least made a down payment on their repeated campaign vows to kill the Affordable Care Act.

Should the bill pass, Ryan, who was first forced to pull the bill in late March, will regain some luster for a speakership that had threatened to go down the same unprofitable path as his predecessor John Boehner -- who was driven to distraction by the recalcitrant conservatives in his caucus.

When he failed to make good on a push to pass Obamacare repeal the first time, Ryan had told reporters that moving from an opposition party, as the GOP was in the Obama years, to a governing party in control of Congress comes with "growing pains."

It will also restore confidence that the GOP can come together to pass an agenda that had been assumed before the health care debacle, to herald a new era of conservative governance.

Before they celebrate...

But the lesson of recent weeks means no House Republican will be complacent. They still need to pass the bill.

Though GOP leaders said they would not put the measure on the floor if they weren't sure they had the votes, there's no cast iron guarantee it passes until the gavel slams down.

One key Republican source close to the health care battle told CNN's Jim Acosta that no one knows for sure if the 216 votes Ryan needs to pass the bill are secure. And the speaker can afford to lose no more than 22 members of his conference if the bill is to go through.

There is an assumption among Republicans, however, that the votes are probably in place since the bill is being brought to the floor.

"I don't think the vote would come today unless it was going to pass," Texas Rep. Michael Burgess told CNN's "New Day" Thursday, but added a caveat that he wasn't on the whip team.

Republican leaders, apparently relieved with forward movement, chose to put on an upbeat face on Wednesday night.

"We're gonna pass it. We're gonna pass it!" Republican House Majority Leader Kevin McCarthy told reporters. "Let's be optimistic about life."

White House Chief of Staff Reince Priebus told CNN's Gloria Borger meanwhile he is "optimistic" about the vote.

Ready to give vote and move on

Despite their optimism, there's an undeniable air of fatigue and desperation surrounding the vote.

Many on the Republican side seemed so wrung out by weeks of tension and brinkmanship they are ready to offload the whole issue to the Senate.

Forcing their hands was the knowledge that every week that the bill languished in limbo, it became more and more likely that Obamacare would survive in its present form.

"We're close here on this and then part of it is as the calendar ticks over another page or two, we either get something done or we live with Obamacare," said Iowa Rep. Steve King, before the scheduled vote was announced.

Flores said the bill had been tinkered with just enough to move some wavering members.

"Some people think it's moved enough to justify an affirmative vote," he said.

But the vote on Thursday will still be a leap in the dark for many Republicans.

There's no certainty that the hard won compromises on preserving coverage for pre-existing conditions will actually work, or even survive the overhaul the Senate is expected to perform when it picks up the legislation.

Critics say the bill would deprive millions of people of coverage and roll back popular provisions of the Affordable Care Act. The bill is opposed by a long list of seniors and health industry lobby groups on the grounds that it curtails coverage.

It's also a risky vote since Democrats are certain to brand Republicans in favor of the bill as voting to take away the health coverage that millions of Americans secured under Obamacare. In that narrow political context, GOP counter arguments about the rising cost of premiums and deductibles may be less potent.

The vote is taking place before the Congressional Budget Office has signed off on costs and coverage of the measure. A previous version of the bill did get a CBO score however, which suggested that 24 million fewer Americans could be insured by 2026 than under the current system, pointing to the long term damage Thursday's vote could inflict on GOP lawmakers.

Burgess, however, dismissed that analysis.

"Yes, the CBO coverage numbers were, to say the least, disappointing," he said, but added: "I disagree with the derivation of some of the numbers. I don't think they accurately predicted human behavior."

The bill as it stands represents a delicate balancing act between conservatives who say the original bill was essentially "Obamacare Lite" and moderates who feared they would be blamed for signing away popular parts of the existing law.

Even the White House admitted Wednesday that no one could know whether the $8 billion in extra cash for high-risk insurance pools used to buy wavering GOP votes was enough. Some independent analysts say it's woefully short.

But if the bill passes, Republican House leaders at least can feel their job is partly done and can begin to envisage more palatable items on their agenda, including a push for a generational tax reform.

And they can wash their hands of health care for a while. They won't for now at least think of the tough conference negotiations that are inevitable when the Senate has had its way.

And Democrats are already setting up 2018 challenges.

Minority Leader Nancy Pelosi, who helped shepherd Obamacare through the House when she was speaker, accused Republicans of gutting coverage and assurances that those with pre-existing conditions could get health care.

"It's a joke. It's a very sad, deadly joke," she said.

Alongside Pelosi, Rep. Rosa DeLauro of Connecticut, an ovarian cancer survivor and Obamacare customer bore witness to the importance of health care coverage for those who have pre-existing conditions.

"This is a very personal fight for me and we will continue this fight ... this is about peoples' lives," she said. "This is about surviving."