Republicans are scrambling to garner support for a plan that will dismantle Obamacare – further evidence that Donald Trump's boast saying that scrapping his predecessor's healthcare law would be easy has fallen flat.

After the Senate narrowly voted to open up debate on a healthcare bill, Republican leaders have suffered multiple setbacks in their efforts to repeal a pillar of former Democratic President Barack Obama's legacy.

In a 45-55 vote, senators have rejected a measure that would roll back major parts of the Affordable Care Act, otherwise known as Obamacare, without a replacement.

On Tuesday night, Republican leaders' most comprehensive plan to repeal and replace the ACA also failed. Senate Majority Leader Mitch McConnell needed 60 votes to move the bill forward, but only received 43. Nine senators from his party defected, a bad sign for Mr McConnell, who is still hoping to pass healthcare legislation by the end of the week.

In the coming days, the Senate is expected to continue debating and take up another proposal that would reportedly roll back three parts of Obamacare: the individual and employer mandates, and the tax that was imposed on medical devices to help fund the ACA.

The proposal is being referred to as a “skinny repeal”, as it is a less comprehensive repeal compared to the bill that failed on Wednesday.

Mr McConnell, who is still expected to receive no support from Democrats, can currently only afford to lose two Republican votes and still be able to pass a bill. The competing interests of Republicans have made this no easy task.

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Mr McConnell may have the toughest time persuading two female Republican senators – Susan Collins of Maine and Lisa Murkowski of Alaska – to support his efforts to uproot Obamacare.

Along with opposing both proposals that failed on Tuesday night and on Wednesday, the two senators were the only members of Mr McConnell’s party to vote against beginning debate on the healthcare bill.

Ms Collins has repeatedly balked at the measure’s significant cuts to Medicaid, which would likely cause millions to lose their health insurance. The repeal-and-replace proposal also included a provision that would defund Planned Parenthood for a year – a proposal that both Ms Murkowski and Ms Collins have taken issue with.

“We had two Republicans that went against us, which is very sad, I think,” Mr Trump said after the Senate voted to open debate on the healthcare bill. “It's very, very sad – for them. But I'm very, very happy with the result. I believe now we will, over the next week or two, come up with a plan that's going to be really, really wonderful for the American people.”

The President has called Obamacare a “nightmare”, and has spent the last week cajoling and seemingly even threatening senators to support his party's healthcare bill. During his presidential campaign, Mr Trump promised to repeal and replace the ACA.

While about 20 million people gained health insurance coverage through Obamacare, Republicans say the law has driven up premiums and forced consumers to buy insurance they do not want and cannot afford.