Hell hath no fury like an American president scorned by members of his own party, Donald Trump seemed to suggest this week in a Twitter tirade.

If only the objects of his wrath, the Freedom Caucus, had reason to worry.

The partisan turf war involves the ragtag group of far-right Republicans who refused to support Trump's American Health Care Act. On Thursday, he threatened to dash their 2018 re-election chances as punishment for derailing his push for health-care reform.

But instead of atoning, the ultra-conservative agitators responded to Trump's words with gleeful taunting. The president communicated his displeasure on Twitter Thursday night.

The Freedom Caucus will hurt the entire Republican agenda if they don't get on the team, & fast. We must fight them, & Dems, in 2018! —@realDonaldTrump

To which Michigan congressman Justin Amash shot back:

It didn't take long for the swamp to drain <a href="https://twitter.com/realDonaldTrump">@realDonaldTrump</a>. No shame, Mr. President. Almost everyone succumbs to the D.C. Establishment. <a href="https://t.co/9bDo8yzH7I">https://t.co/9bDo8yzH7I</a> —@justinamash

Congressman Justin Amash, speaking in Battle Creek, Mich., is a member of the Freedom Caucus who stands up to Trump on Twitter. (Associated Press)

Fellow Freedom Caucus member Thomas Massie, a representative from Kentucky, piled on, aping Trump's Twitter style.

.<a href="https://twitter.com/realDonaldTrump">@realDonaldTrump</a> it's a swamp not a hot tub. We both came here to drain it. <a href="https://twitter.com/hashtag/SwampCare?src=hash">#SwampCare</a> polls 17%. Sad! <a href="https://t.co/4kjygV2tdS">https://t.co/4kjygV2tdS</a> —@RepThomasMassie

Representative Thomas Massie watches a live downlink with American astronauts in 2014. He apes the president's tweeting style. (Yuri Gripas/Reuters)

Congressional experts struggled to make sense of why Trump risked alienating the Republican faction, given the math in the House. More than 30 members are believed to comprise the House Freedom Caucus, out of 240 Republican seats. Trump's bills wouldn't reach the 218 votes needed for passage without the bloc's support.

"On any issue of which the Republicans have given up on securing votes, the Freedom Caucus is pivotal," said Sarah Binder, a senior fellow in governance studies at the Brookings Institution.

It's also clear they know their defiant role, which supports measures observing pure conservative orthodoxy, makes them power brokers in the lower chamber.

'Lawmakers were not cowed'

"Lawmakers were not cowed by [Trump's] tweets. The Freedom Caucus folks were pretty blunt. They were not shying away."

The defiant Republicans represent districts in solidly red states. Many of those legislators were Trump defenders during the presidential campaign.

Many also outran Trump in their districts. Their re-election chances in the 2018 midterms would appear safe, despite Trump suggesting he might back primary challengers to oppose them.

Days before the vote collapsed last Friday, the president visited the Capitol. He told Freedom Caucus chairman Mark Meadows his bloc had better fall in line. Trump wanted Meadows to endorse the health bill.

Or else?

House Freedom Caucus Chairman Mark Meadows smiles as he speaks with the media on Capitol Hill on Thursday. Trump told Meadows his bloc had better endorse his health bill. It didn't. (Alex Brandon/Associated Press) "Mark, I'm coming after you," Trump warned, according to the Hill Times.

Congressional experts argue condemning members for their intransigence only after the failure of Trump's health bill makes little sense now that the political moment for health-care reform is gone.

"He's making an empty threat," says Stan Brand, a former general counsel to the House of Representatives who served during Democratic Speaker Tip O'Neill's tenure from 1978 to 1983. "These Freedom Caucus guys just don't see themselves as vulnerable."

Trump has no leverage

Trump's problem is he doesn't have any leverage in the form of political capital, says Alan Wiseman, a Vanderbilt University professor who has researched legislative strategy and effectiveness in Congress.

The president faces historically dismal poll numbers, a conservative opposition whose popularity in their districts surpasses his, and a disinclination to strike deals with Democrats in a deeply polarized Congress.

"A reasonable interpretation for what he's doing is that he and his advisers believe that his policy agenda really represents the will of the constituents of the Freedom Caucus," Wiseman says. "By going public with his displeasure of the Freedom Caucus, I'm assuming that he assumes his constituents will put increased pressure on them to bargain with the president."

That strategy could also "backfire dramatically," Wiseman adds, as many of the Freedom Caucus members already enjoy strong local backing.

'Their constituents may be bothered'

"For the president to antagonize them to change their opinion, if their constituents are entirely happy with how they're representing their views, then Trump is not going to make any headway," he says. "Their constituents may be bothered by these tactics."

Trump's legislative landscape looks rough. Research has long shown that a president's influence over Congress is closely related to public approval ratings.

For a president to get members of Congress to vote for things they don't want to vote for, the president has to at least be popular. — Prof. Alan Wiseman

Wiseman notes Trump's poll results are hardly inspiring. His support dipped to 35 per cent in a Gallup Daily Tracking survey last week.

"For a president to get members of Congress to vote for things they don't want to vote for, the president has to at least be popular," Wiseman says.

Without adequate political cover, Republican representatives would have no incentive to back the president's agenda, says Molly Reynolds, a senior fellow in governance studies with the Brookings Institution.

She sees a certain irony at play, noting that Trump is being restrained by the very anti-establishment forces that helped vault him to the White House. Since its inception in 2015, the Freedom Caucus has had a mindset of persistent opposition while a Democratic president, Barack Obama, was in charge, Reynolds says.

From darling to foe

Its resistance now to Trump is "consistent with the identity the Freedom Caucus fashioned for itself," Reynolds says. Only now, the president — the darling of anti-establishment Republicans in 2016 — is opposing the anti-establishment Republicans of 2017.

"So much of what the Freedom Caucus tried to do over time was hold the House leadership's feet to the fire. I'm not terribly surprised some of them have a similar posture towards Trump."

Now that Republicans control both chambers and the White House, Reynolds says, "they're having to make this transition from being an opposition party to being a governing party."

"As for what does that mean in an era that has party control? I think they're still trying to figure that out."