President Donald Trump’s hard-fought healthcare victory could backfire, as House Republicans that voted to repeal Obamacare are now vulnerable to backlash from their constituents.

The Republicans’ 217-213 passage of the American Health Care Act (AHCA) hurts the re-election chances of several representatives who supported the bill, according to the Cook Political Report.

The non-partisan election analyst changed its forecast in 20 House districts, deeming each of them more likely than before to be won by a Democrat. The analyst also re-labelled three seats leaning Republican to ‘toss-up’.

“House Republicans' willingness to spend political capital on a proposal that garnered the support of just 17 per cent of the public in a March Quinnipiac poll is consistent with past scenarios that have generated a midterm wave,” according to the group.

Twenty Republicans voted against the AHCA, which received no support from Democrats.

As it became clear during Thursday's vote that the bill was going to pass, Democrats began taunting members of their rival party by singing “Na na na na, na na na na, hey hey hey, goodbye”, the lyrics to a 1969 song by Steam, which is often heard at sporting events. Democrats warned Republicans that they would pay the price in future elections if they followed through with plans to dramatically alter healthcare law.

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House minority leader, Democrat Nancy Pelosi said the AHCA will provide a great civics lesson for America.

“Let's face it, as important as we think we are when we're in Congress, most people don't even know who their Congress person is in many places, and now they'll find out,” Ms Pelosi said. “They'll find out that their Congress person voted to take away their healthcare.”

Following the vote, the House Democratic campaign arm announced that it would immediately begin launching ads in 30 Republican-held districts, regardless of whether the politicians holding them had voted for the bill.

“The ads will run on Facebook and Instagram in order to expose what is in this bill and why it’s a terrible deal for hardworking Americans,” the Democratic Congressional Campaign Committee said in a statement. “This is just the beginning of a robust ad campaign with more to come next week.”

Mr Trump has emphasised that the Republican bill is “a great plan”, and says that it will get “even better”. He has vowed that premiums and deductibles will decrease.

Despite passing in the House, the AHCA still faces an uphill battle in the Senate, where several Republicans have said that they will look to write their own proposed law instead of picking up the lower chamber’s.

During the daily White House briefing, deputy press secretary Sarah Huckabee Sanders said that the Trump administration expects the Senate to make some changes, “but we expect the principles and the main pillars of the healthcare bill, as it exists now, to remain the same”.

She later added that Mr Trump will continue to be “hands-on” in the process.

“He was fully engaged on the House side,” Ms Sanders said. “I expect him to fully engage on the Senate side.”

Senate Majority Leader Mitch McConnell seems to not be backing a total re-write of the bill. He has assembled a working group to try to find a consensus, and has said that the Senate will wait for the Congressional Budget Office (CBO) to release its analysis of the AHCA before scheduling a vote.

Trumpcare opponents have criticised House leadership for not allowing the CBO to finish analysing how much the AHCA would cost, or how many it would affect, before holding a vote – a sign that the leaders were trying to rush the bill through the lower chamber, they said.

Meanwhile, Senate health committee chairman Lamar Alexander said in a statement that “the Senate will now finish work on our bill, but will take the time to get it right”, echoing remarks made by majority whip John Cornyn, who said, “We're not under any deadline, so we're going to take our time.”