Roughly 20 centrist Republicans say they are opposed to a bill that would repeal and replace Obamacare, but few have articulated specifically what would need to be changed in the legislation to bring them to a "yes" vote.

Though most say they favor Obamacare repeal, when faced with the possibility they have shunned the legislation, the American Health Care Act, in its current form or when changes have been presented.

Centrists broadly say either that the bill fails to protect Medicaid recipients, the majority of whom are low-income, or to protect people with pre-existing conditions. A few say both of these components will fail to earn their "yes" vote.

"Each of us is evaluating it individually based on the commitments we've made," said Rep. Ryan Costello, R-Pa.

He said it would be problematic to bring a bill to the House floor that would contradict statements he has made, some of which raise concerns for constituents who have pre-existing conditions.

Rep. Mark Amodei, R-Nev., wrote in his weekly newsletter that his opposition to the bill centered on planned cuts to the Medicaid program, which was expanded to cover low-income people through in his state under Obamacare.

"While I will continue to keep an open mind, if the current plan is the bill that comes to the floor for a vote — I will not be supporting it," he wrote.

In March, before more recent changes were proposed, Rep. Barbara Comstock, R-Va., who opposes Obamacare, said in a statement that "the uncertainties in the current version of the [repeal and replace] bill caused me not to be able to support it."

On Tuesday she declined to answer further questions about the bill, saying that she had already stated her position.

Others say compromise with Democrats should occur, like Rep. Leonard Lance, R-N.J., who told NPR in March that he did not think the bill lowered premiums or covered enough people.

Republicans can afford to lose no more than 22 votes to guarantee the bill's passage in the House. GOP leaders have said that they do not have a floor vote scheduled or a deadline in mind, but some have speculated that they will want a vote ahead of a one-week recess that begins Thursday.

When the first deadline to pass the bill failed in March, attention centered on the conservative House Freedom caucus, whose individual members opposed the bill because they said it did not go far enough in repealing Obamacare. Its members offered a specific list of what it wanted to see changed to win over their support.

The eventual agreement resulted in an amendment authored by Rep. Tom MacArthur with feedback from Freedom Caucus chairman Mark Meadows, R-N.C. Dubbed the MacArthur Amendment, the change would allow states to apply for waivers to opt out of Obamacare mandates, including one that requires insurance companies charge sick or healthy customers the same amount if they are the same age.

Critics of the plan say that it essentially does away with protections for people with pre-existing conditions by allowing insurance companies to charge exorbitant rates. Defenders, however, note that states could not waive the provisions unless they set up high-risk pools, which would be federally funded.

Republicans worry about the political consequences of voting for a bill that is likely to undergo major changes in the Senate, particularly because the party vowed to protect patients with pre-existing conditions from being denied coverage.

"I think it's a responsibility for me to be a staunch advocate for protecting people with pre-existing conditions," said Rep. Brian Mast, R-Fla.

Others have said they are undecided. Rep. Rob Wittman, R-Va., for instance, says he is mulling over the MacArthur Amendment.

Comments by President Trump have suggested that the bill is still up for negotiation.

"I want it to be good for sick people," Trump said in a Bloomberg interview. "It's not in its final form right now. It will be every bit as good on pre-existing conditions as Obamacare."

Some Republicans say even more negotiations are occurring. Rep. Phil Roe, R-Tenn., hinted that he could propose changes next week on pre-existing conditions, but wouldn't elaborate on the details. MacArthur said Republicans are talking about adding more funding for high-risk pools.

That approach wouldn't satisfy all Republican lawmakers opposed to the American Health Care Act. Reps. Fred Upton of Michigan and Charlie Dent of Pennsylvania have said it would not bring them to "yes," according to reports.

Rep. Ileana Ros-Lehtinen, who had been opposed to the repeal bill ahead of the most recent changes, because of projected Medicaid cuts, said that the latest changes still put her at a "no" vote.

"It's tough for pre-existing conditions and was just a fig leaf," she said of the amendment.

Washington Examiner's Robert King and Al Weaver contributed to this report.