President Trump has told Republican leaders that he's prepared to play hardball with congressional conservatives to pass the GOP healthcare bill, including by supporting the 2018 primary challengers of any Republican who votes against the bill.

Sources told the Washington Examiner that Trump made that threat in a White House meeting on Tuesday with House Majority Whip Steve Scalise, R-La., and other members of the House GOP whip team that helps line up votes.

Trump's threat is one that could resonate. Most of the Republicans who oppose the GOP's American Health Care Act represent ruby red districts that strongly support Trump and his agenda.

Therefore, they could be the most susceptible to a midterm primary challenge, especially if Trump tells those voters that their member of Congress is blocking him from fulfilling his promise to repeal President Obama's healthcare law.

"The president will respond as circumstances dictate," a House Republican said Friday, on condition of anonymity in order to discuss internal strategy. "He has unique capacities; I wouldn't want to be the one he tests them out on."

If negotiations don't reach fruition as the bill readies for a floor vote, Republican insiders said, watch Trump's tweets and travel schedule for signs that he's dispensed with the carrots and brought out the stick to try to get wayward members on board.

Party insiders say the president at that point could choose to make an example of one or two resistant Republicans to send a message.

Rep. Mark Meadows, chairman of the Freedom Caucus, the primary group of House Republicans opposed to the healthcare bill, is a possible target. His western North Carolina district voted overwhelmingly for Trump in November, and Meadows has come out in opposition to the bill.

Meadows was still opposed this week but seems to recognize that it would be difficult to win an argument with the president at home.

"The president has a very powerful bully pulpit and a very powerful tweet and so I would never want to take on the president in either of those realms," he admitted.

Trump so far has deployed the carrot in a bid to persuade the opposition to his side. Rep. Tom Cole, R-Okla., a member of the House deputy whip team, said that might be enough.

"I don't think he has to threaten them. I think he does have to persuade them and make them realize, we fail at this, the first victims are going to be you guys, because you're the ones up in 2018," Cole said. "People have to decide, do you really want to hand the president a defeat on his first major initiative? I think that's full of political consequences for people that do it."

Trump continues to negotiate with opposition conservatives to improve the bill and gain their support, although the administration and Republican leaders are ruling out many of the major changes critics are demanding.

Trump has held listening sessions with conservative advocacy groups that oppose the bill, and tried publicly to encourage Sen. Rand Paul, R-Ky., to drop his opposition. He's also dispatching Vice President Mike Pence to Louisville on Saturday for a rally with Gov. Matt Bevin to drum up support.

Trump first road trip to sell the health care bill is scheduled for next week in Nashville.

The whip team was expected to present Trump with a list of Republicans that need convincing on Tuesday. That's when they are next scheduled to meet at the White House, in what is to become a weekly check-in session until the House passes health reform.

The White House said Friday in an email exchange that the president is heavily engaged in trying to forge consensus and push the bill through Congress.

"This includes various meetings, such as the several meetings with legislators and activists at the White House, working alongside House and Senate leadership, and continued outreach to various coalitions," a spokesman told the Examiner.

Conservative critics of the health care bill are dismissing it as "Obamacare-lite." They say it doesn't go far enough in unwinding the Affordable Care Act or implementing free market reforms that would reduce premiums and improve access to quality care, and many are asking for a clear repeal bill, and then a fresh debate on its replacement.

But for Trump, that is simply a nonstarter.

Republican leaders on Capitol Hill and the Trump administration say the GOP faces a binary choice. Pass the AHCA, possibly with some minor alterations, and fulfill their years-long promises to repeal and replace Obamacare, or let the opportunity pass and bear responsibility for a failing to fix health care.