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The once-sidelined Republican effort to repeal and replace Obamacare received a shot of momentum Wednesday as a group of conservative House Republicans came out in support of the bill after proposed changes to the underlying legislation.

The announcement by the Freedom Caucus changes the dynamics of the discussion and could provide enough votes for House Republicans to pass the measure.

"While the revised version still does not fully repeal Obamacare, we are prepared to support it to keep our promise to the American people to lower healthcare costs," the Freedom Caucus, a group of three-dozen members, said in a statement.

But while some conservative members of Congress giving support to the measure, the proposed changes are also raising new concerns about some of the promises the party has made about guaranteed, affordable coverage and even how members of Congress themselves would be treated.

And moderate Republicans are expressing concern about the changes that they say could increase costs and limit coverage options for those who are sicker.

Still, Republican leadership says the momentum is a good sign in the prospects of the bill's passage.

“The good news is a lot of really good progress has been made during these last two weeks. A lot more members are focused on getting to where we need to be,” said Rep. Steve Scalise, the third-ranking Republican in the House responsible for counting votes. “And so we're not going to stop working until we get that done.”

Rep. Patrick McHenry, R-N.C. a deputy whip, sounded optimistic Wednesday afternoon about the bill's imminent passage, saying "It’s a question of timing."

But the timing for a vote is fluid. Republican leadership won't bring it up for a vote until they are confident is has enough support to pass. A vote could happen as early as this week, said senior Republican aides, but others say it could happen next week.

The original Republican bill was dropped even before it came up for a vote last month after leadership was unable to obtain enough votes for passage. Both conservative and moderate members objected to the original legislation and negotiators have been working on changes for the past weeks.

The new proposed amendment, authored by Rep. Tom MacArthur, R-N.J., is an attempt to appease some of the conservatives by allowing states to get a waiver for regulations on insurance companies that protect patients, such as equal-cost coverage for those with pre-existing conditions and a robust benefits package known as essential health benefits, but that also, they say, increase the cost of coverage. States must show that people with high health care costs will be covered, either through a high-risk pool or a federal cost-sharing program.

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“I believe that we’re going to get to 216 or beyond,” said Rep. Mark Meadows, R-N.C, chair of the Freedom Caucus, which was largely responsible for sinking the first attempt at health care last month. He was referring to the number of Republicans it will take to pass a health care bill in the House.

Rep. Scott Desjarlais, R-Tennessee, a member of the Freedom Caucus and was opposed to the bill, said this new change is productive.

"I think it looks pretty good," he told reporters Monday night.

And Rep. Dave Brat, R-Virginia, who was also a critic, said that he is now “looking forward” to voting for the bill.

But in an attempt to appeal to conservative, the new amendment back-tracks on a Republican campaign promise to keep coverage for those with pre-existing conditions. The measure could allow insurance companies to charge people with pre-existing conditions more, a component likely to be unpopular among moderates, especially those from Democratic or swing districts.

Rep. Mike Coffman, R-Colo., who was supportive of the bill last month, said he's now concerned about the changes.

"I made it very clear … that I’m going to protect pre-existing conditions," Coffman told reporters. "This is a fairly complicated proposal so I gotta review it."

"I am a no,” said Rep. Leonard Lance, R-N.J., after the proposed changes.

Pennsylvania Republican Rep. Charlie Dent, told reporters of the changes: “It doesn't address my underlying concerns."

The latest round of negotiations is also further splitting the Republican conference. Some moderates are frustrated that there's been so much focus on conservatives' concerns. And conservatives have been frustrated that they've been blamed for the bill's first-round failure.

Dent said this conservatives' support of the amendment is an attempt at "blame-shifting."

"It means that a lot of them were taking a lot of heat for the failure of the bill," Dent said.

Meanwhile, conservatives are labeling their moderate colleagues as "liberal" or "left-of-center."

"Unless there is major dissent by some of the moderate, or really left-of-center members ... I think this will probably make a difference," said Rep. Trent Franks, R-Ariz.

The measure ran into a new problem just hours after the text of the legislation was released, however. The amendment protects members of Congress and their employees from those waivers on pre-existing conditions and essential health benefits. In other words it keeps some of the most popular parts of Obamacare for members of Congress.

The development was first reported by Vox Wednesday morning and House Republicans immediately addressed it in their closed-door conference meeting.

They emerged from the meeting insisting that, that because of strict Senate rules to pass the health care bill on a mechanism known as reconciliation, the House bill must retain the protection for members of Congress and the Senate will have to fix it once they get the bill.

Republican leadership has said that they will schedule a vote for the bill once they have the votes. A vote is not currently scheduled.

This amendment is part of a larger bill that would unwind Obamacare and all of its taxes, including the tax on couples making more than $250,000. In its place, the American Health Care Act gives tax credits to people who purchase health insurance outside of an employer based on age instead of income. It would also end the Medicaid expansion and cap the number of Medicaid recipients based on the state’s population.

Democrats are already preparing attacks on Republicans for supporting this new version of the bill.

“Removing protections for people with pre-existing conditions will go down in infamy as one of the most heartless acts of this Republican Congress,” said Tyler Law, spokesman for the DCCC, the campaign arm of Congressional Democrats. “As proof of the repeal bill’s devastating impact, Republican Members of Congress are exempting themselves from the punishment they are willing to inflict on their constituents.”

And not all Republicans are on board, including, Rep. Thomas Massie, R-Kentucky.

"I went from a hell no to a no," Massie said.