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House Republican leaders plan to hold a vote on their health care bill Thursday, sending the strongest signal yet that enough support has been corralled to pass it.

Asked whether they had the votes needed to pass the bill, House Majority Leader Kevin McCarthy of California said Wednesday night, "Yes, we do."

"I feel great about the count," McCarthy added.

Republicans have been working to piece together a GOP-only coalition of 216 votes ever since their attempt to repeal and replace much of the Affordable Care Act failed nearly two months ago. The House Rules Committee approved three major amendments Wednesday night, moving them along in time for a vote Thursday.

Rep. Tom MacArthur, R-New Jersey, the author of one of the amendments, told NBC News: "It's not a perfect bill — nobody says it is — but directionaly it's going in the right place."

The latest iteration of the American Heath Care Act aims to protect those with pre-existing conditions by adding $8 billion for five years to help people with long-term health issues afford care. Health care experts, however, say the amount is too little to address the needs, and several patient advocacy groups have come out against the bill.

Some members thought the additional funds were needed because of a previous change that would allow states to opt out of insurance mandates required by Obamacare that protect patients and consumers but that some conservatives blame for rising health care costs.

In the new version of the bill, states would be able to opt out of the requirement that insurers cover benefits such as maternity care, mental health care and hospitalization

And states that obtain waivers could charge those with pre-existing conditions much more. States would have to be able to show a mechanism for people to get coverage, such as high-risk pools. The Republican bill would provide $125 billion to help pay for the pools' high costs.

Related: Here's Where the GOP Vote Count Stands

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The White House and Republican leaders have spent the week putting on a full court press, holding numerous meetings and phone calls with members who are undecided or said they were against the bill. President Donald Trump has been personally lobbying lawmakers.

Vice President Mike Pence was on Capitol Hill every day this week, speaking to members individually to persuade them to vote for the bill.

Those efforts must have proven fruitful, because leaders had said they wouldn't hold a vote until they had enough votes to pass the measure.

A senior White House official called the impending vote "a positive development."

House Democratic leader Nancy Pelosi of California said House Republicans would now be identified with the provisions in the bill.

"From the beginning, Trumpcare has meant higher health costs, more than 24 million hard-working Americans losing health coverage, gutting key protections, a crushing age tax, and stealing from Medicare," Pelosi said in a statement. "But tomorrow, House Republicans are going to tattoo this moral monstrosity to their foreheads, and the American people will hold them accountable."

Momentum for the bill increased after two members, including the influential Rep. Fred Upton, R-Michigan, former chairman of the Energy and Commerce Committee, said he'd support the bill. He's the one who helped usher in the additional money for those with pre-existing conditions.

As of Wednesday afternoon, 19 lawmakers said they were still opposed to the bill despite the changes, and more than two dozen said they were undecided. But the number seemed to have dwindled.

Two of those members — Reps. Dave Young, R-Iowa, and Jeff Denham, R-California — have said they were opposed, but they came out as co-sponsors of the Upton amendment, sending a message of support.

Health policy experts, however, said the additional $8 billion would not offset the cost of people with pre-existing conditions.

"This is a drop in the bucket," Matthew Fielder, a fellow at the Brookings Institution, told NBC News.

The AARP and several other patient advocacy groups have come out in opposition to the bill, claiming it would harm patients.

The complaints by Republicans came mostly from moderate Republicans who feared too steep cuts to Medicaid, high costs for those with pre-existing conditions, and too few resources for mental health needs and opioid addiction treatment.

Moderates were frustrated because many of the changes made to the bill were to accommodate conservatives' concerns. Previous additions to the bill would have phased out Medicaid much more quickly and put in work requirements for most able-bodied people who aren't the primary caregivers for children under the age of 6.

Republican leaders and the White House tried to address some concerns by promising to address members' health care priorities.

For instance, Republicans leaders promised Rep. Paul Gosar, R-Arizona, a vote on his bill that would reinstate the enforcement of anti-trust laws on insurance companies.

Members who aren't enthusiastic about the bill also had hopes that the Senate would make it more palatable.

Rep. Peter King, R-New York, said he's voting on it to "move the bill forward."

If the House passes it, the Senate would then try to pass the measure, but it would likely look much different coming out of the more moderate upper chamber.

Even with the changes in the past week, the non-partisan Congressional Budget Office will not analyze the bill for how much it will cost the federal government or its impact on consumers, Republican lawmakers said — raising sharp objections from Democrats.

"This process, to put it bluntly, is a godd--n mess," Rep. Jim McGovern, D-Massachusetts, told NBC News.

The bill would also repeal all of Obamacare's taxes, including a tax on couples making more than $259,000 per year. It would replace subsidies based on income with tax credits based on age to help people purchase insurance in the individual marketplace.

They are hoping to pass the bill before members head home for 12 days and can tell their constituents that they delivered on a multi-year campaign promise to repeal Obamacare.