Donald Trump issued an ultimatum to Republicans Thursday night: Vote for my health care bill, or else. The “or else” in this case would mean being “stuck with Obamacare,” but as many GOP representatives still struggle to come around to voting for a bill which has had very little public support, the president could be in for the most embarrassing defeat of his administration to date.

A vote on the American Health Care Act — the first part of the Republicans’ plan to repeal and replace Obamacare — was due to take place Thursday, but after heated discussions between the administration and House Republicans, it became clear that the vote would not pass, and so it was postponed.

Late Thursday night Trump sent top administration officials to the Capitol to deliver his ultimatum, and a vote is now scheduled to take place Friday morning. Should it fail to pass, reports suggest the president will leave Obamacare in place and move on to other areas of legislation, including tax reform and infrastructure spending.

But make no mistake, Trump is playing a dangerous game by forcing a vote on Friday. A defeat would mean he’d failed to deliver his first key piece of legislation and let a key campaign pledge slide. It would be seen as hugely embarrassing for the president.

When asked whether Republicans would pull together Friday, Congressman Matt Gaetz told the Associated Press: “I sure hope so, or we’ll have the opportunity to watch a unified Democratic caucus impeach Donald Trump in two years when we lose the majority.”

Here’s what you need to know:

Trump on Thursday night made one major concession to try to persuade the influential group of Republicans known as the Freedom House Caucus. In a rule written overnight, the bill will now get rid of Obamacare’s “essential health benefit” requirements — coverage for basic medical care such as pregnancy and maternity care, mental health and addiction treatment, and lab tests — that were untouched in the original bill.

“We have been promising the American people that we will repeal and replace this broken law because it’s collapsing and it’s failing families, and tomorrow we’re proceeding,” House Speaker Paul Ryan told reporters on Thursday night. He ignored questions about whether the party had secured enough votes to pass the bill. Representative Chris Collins, a close Trump ally, said, “The president has said he wants a vote tomorrow, up or down.”

The vote was specifically planned to take place Thursday as it marked the anniversary of when former President Barack Obama signed Obamacare — officially the Affordable Care Act — into law in 2010.

Because of united Democratic opposition in the House, if more than 22 Republicans vote “no,” the bill won’t pass. As of Thursday evening, the New York Times reported, 33 were committed to voting “no” with 15 more listed as uncommitted or leaning that way. CNN puts the figures at 27 voting “no”, and another four leaning that way. The Washington Post had the “no” votes as high as 35.

However, on Thursday night, White House sources speaking to Axios said they believe the vote is close, and getting Freedom House Caucus chairman Mark Meadows on board will give them the necessary momentum.

The problem is that Meadows, as of Thursday night, was still a “no“ and in order to get him to come around, it would require the bill to go much further than it does in its current form. The Meadows plan would include getting rid of things most Republicans said they would never touch, such as the ban on annual and lifetime limits on health benefits.

It’s no surprise that Trump is struggling to get enough Republicans onside. According to a Quinnipiac poll published Thursday, just 17 percent of respondents approve of the bill – a remarkably low figure.

Adding to the perception that the new bill will make people worse off was a revised Congressional Budget Office score for the amended version of the legislation, which was issued late Thursday night. It stated that even with the amendments, it would still lead to 14 million fewer people having health insurance in 2018 than would be covered if Obamacare remained as law in its current form. That figure would rise to 24 million by 2026. The amended bill would cut federal spending by $150 billion, less than half the savings predicted for the original bill.