Paul Ryan's plan to repeal and replace Obamacare is expected to come out soon - here are the biggest fights he'll face

House Speaker Paul Ryan and the House GOP leadership are expected to roll out their plan to repeal and replace the Affordable Care Act (ACA), known as Obamacare, sometime over the next few days.

The bill will be moved through a process known as budget reconciliation, meaning it would only influence the parts of the ACA that have to do with federal funding. It would pertain to massive parts of the law including Medicaid expansion, the mandate that everyone must buy insurance, and all taxes and tax credits under the law.

One of the perks of this process for Republicans: They only need a simply majority in the Senate to pass the bill, avoiding an all-but-certain filibuster by Democrats.

While the plan that has emerged in bits and pieces in recent weeks has the backing of many prominent members of the House, there is no guarantee that it will make it unscathed - or at all - to President Donald Trump's desk.

Groups on the right and left of the political spectrum have gripes with Ryan's plan - and how those battles are fought will ultimately decide the fate of the ACA and millions of Americans' health insurance.

Moderate objections

One of the biggest fights that face Ryan and Republicans are changes to the ACA's Medicaid expansion.

Under the ACA, states receive significant funding to grow the Medicaid program that provides health insurance to Americans living in or close to poverty. So far, 34 states and the District of Columbia have taken up the offer.

A leaked draft of the House GOP's Obamacare replacement bill would shift funding for Medicaid expansion to block grants, chunks of funding that most health policy analysts say would increase the funding burden for states.

The problem: Senators in states that have expanded Medicaid have found the program to be popular, and roughly two-thirds of Americans nationwide support the expansion, according to recent polls.

Sen. Lisa Murkowski of Alaska has said that she will not vote for a bill that defunds the Medicaid expansion or shifts it to a block-grant system.

Other Republican senators in states that have expanded Medicaid have also expressed concerns about maintaining coverage for those people who now have insurance through the program. Just over 11 million Americans that otherwise would not have coverage have gained insurance through Medicaid expansion, according to estimates from the Kaiser Family Foundation.

Sen. John Thune of South Dakota called the Medicaid expansion the "the thorniest and most difficult issue to resolve."

A number of Republican governors have also come out against a repeal of the Medicaid expansion. Perhaps the most vocal has been former Republican presidential candidate and Ohio Gov. John Kasich.

Kasich met with Trump recently to explain the value of maintaining the status quo for Medicaid expansion and has called rollback of Medicaid expansion a "very, very bad idea."

Additionally, Doug Doucey, the Republican governor of Arizona, expressed misgivings about proposed Medicaid funding changes in a letter to Congress. He said the proposed "policy change will result in the single largest transfer of risk ever from the federal government to the states."

Finally, states with Republican governors including Kansas, North Carolina, and Maine have all expressed a desire to expand Medicaid themselves.

Conservative pushback

While more moderate Republicans have been in favor of keeping some of the ACA's provisions for Medicaid, the right flank of the GOP has been saying that the leaked repeal plan does not go far enough.

Members of the House and Senate have called the proposal "Obamacare-lite" and have said that it does not fulfill the Republican promise to get rid of the law.

Rep. Mark Meadows, head of the conservative House Freedom Caucus, said he would not vote for the bill in the leaked form. (That leaked bill was a draft version, so changes could have been made in the interim.) Meanwhile, other House members appeared to push back on the plan.

Rep. Mark Walker, the head of the Republican Study Committee, also said in a statement that the current proposal was inadequate.

"There are serious problems with what appears to be our current path to repeal and replace Obamacare," Walker said. "In that form, and absent substantial changes, I cannot vote for the bill and, in good conscience, cannot recommend RSC members vote for it either."

For these members, the biggest issue has been the tax credits given out to Americans to buy health insurance. Conservative Republicans have argued the federal government shouldn't be involved in funding the credits.

This is a concern shared by conservative members of the Senate. Sens. Rand Paul, Ted Cruz, and Mike Lee have all come out against the House plan, saying it does not go far enough in its repeal.

In a tweetstorm on Thursday, Paul criticized the plan and the House GOP leaderships strategy of keeping the bill a secret by placing it in a secure room only available to certain Republican lawmakers.

"What is the House leadership trying to hide?" Paul said. "My guess is, they are trying to hide their 'Obamacare Lite' approach. Renaming and keeping parts of Obamacare, new entitlements and extending medicaid expansion are not the #FullRepeal we promised."

Democratic opposition

Not only do Republicans have problems within their own party, but passage also won't be any easier given Democrats' plan to oppose the GOP at every turn.

Senate Minority Leader Chuck Schumer and House Minority Leader Nancy Pelosi have made it clear that they have no plans to cooperate on repeal and replace legislation. Even former President Barack Obama told Democratic lawmakers in a closed-door meeting right before he left office not to "rescue" Republicans in their attempts to repeal and replace the ACA.

Democrats do not control either chamber of Congress and have little power to stop any reconciliation bill without Republican defections, but the internecine warfare in the GOP could complicate things for the party. Given the thin margin Republicans hold in the Senate (52 to 48), only a few defections from the GOP and a united front from Democrats (and the two independent senators who nearly always vote with them) would defeat any repeal bill.

Even a coalition of Paul, Cruz, and Lee voting with Democrats against a bill (albeit for vastly different reasons) would be enough to halt it.

The internal GOP arguments led Schumer to say that he does not even think the Republicans can advance an ACA replacement. He tweeted before Trump's address to Congress that "the odds are very high that we'll keep the ACA."

Trump wild card

The final fight is one against the uncertain policy goals of Trump himself.

While Trump laid out a vision for healthcare in his speech to the joint session of Congress that followed along the outline of the leaked House GOP plan- especially the call for tax credits, directly rebuking the conservative wing of the party - uncertainties remain that could throw a wrench in the repeal and replace plans.

Reports from The Washington Post said Trump seemed open to Kasich's plan for keeping Medicaid expansion and the president has at times shifted positions on his healthcare goals.

Additionally, Trump has made some big promises when it comes to the law. He has said that the plan will eventually cover all Americans, be cheaper than the current system, and provide better care overall. Most health policy experts agree that expanding coverage to all people while the government spends less on healthcare is virtually impossible, so it is unclear how Trump will come down in the debate over the ACA's future.