Since the House GOP’s health reform bill was released last week, it’s drawn the loudest Republican criticism from the Freedom Caucus. This group of Congress members, aligned with a few senators, has threatened to oppose the bill because it fails to roll back enough of Obamacare.

That group could, conceivably, kill the bill in either the House or the Senate, if all its members hang together. But another massive threat to the bill comes from a different group of Republicans entirely — those worried a GOP health law would cause too many people to lose health insurance coverage. That group doesn’t have a formal name; let’s call it the Coverage Caucus.

The Coverage Caucus is not an organized bloc in any way, shape, or form. It is a loose collection of Republicans who fear any bill that would result in millions of Americans losing health insurance. Some are worried about their constituents losing health care. Others also worry that voting for such a bill could hurt their political careers.

Those Republicans are, by and large, blanching at the Congressional Budget Office’s estimates that 14 million fewer people would be covered in 2018, and 24 million fewer by 2026, if the American Health Care Act becomes law.

On the normal ideological spectrum, we’d think of this as a critique of the bill from the left. But interestingly, the Coverage Caucus isn’t just moderate Republicans in swing states or districts who are worried about losing their seats to Democrats (though many of them are represented).

Instead, some of its members, like Sen. Bill Cassidy (R-LA), are conservatives from poorer red states that have greatly benefited from Obamacare’s subsidies and Medicaid expansion. Despite a lack of electoral pressure, they rightly fear that their constituents could be greatly harmed by a poorly designed Obamacare repeal-and-replace effort.

The critics from the right have been loudest in the House, but Republican criticisms over coverage losses are growing

It’s not clear exactly how big the Coverage Caucus is, especially in the House. Few GOP representatives have openly made this critique of the American Health Care Act so far, though leaked audio from a Republican retreat in January suggests that many members share these concerns behind closed doors. And in recent days, their numbers have been growing:

Rep. Ileana Ros-Lehtinen (R-FL) tweeted Tuesday that she will oppose the current version of the AHCA because it leaves too many from her district uninsured.

Rep. Rob Wittman (R-VA) — who is in a safe Republican district but may have ambitions to run statewide — announced his opposition to the bill in an attention-getting statement shortly after the CBO score dropped. “All Virginians should be able to purchase health insurance coverage,” he said.

Rep. John Katko (R-NY) said Tuesday that some aspects of the CBO report, including its coverage projections, give him “significant concern” about the AHCA. “There are serious questions that need to be answered,” he said.

Rep. Darrell Issa, who’s expected to be one of the most vulnerable House Republicans in 2018, said the day before the CBO score came out that he’s “not prepared to vote for [the bill] as is.”

Some members have likely been trying not to stick out their necks too early. Some could be expressing their concerns to House leadership in private. Others could be very conflicted but end up voting to support a bill in the end. But with that grim CBO score and the House bill barreling toward a floor vote, they won’t be able to stay undecided forever.

So in the coming days, keep an eye on, for starters, the 23 Republican members of the House representing districts Clinton won, and the other 11 in districts Trump won by 5 points or less, as well as the many more from states that participated in Obamacare’s Medicaid expansion. All these Congress members will likely have at least some concern over coverage losses, and many could vote against the bill for that reason.

The Coverage Caucus is strongest in the Senate

Even if the American Health Care Act gets through the House, though, the CBO score will apparently pose immense problems in the Senate. The margin for passage is much narrower in the Senate — three Republican defections would kill the bill. And many more Republican senators than that have spoken out with concerns about coverage losses:

Sen. Bill Cassidy (R-LA) has said he wants any replacement plan to insure a comparable number of people to Obamacare, as scored by CBO.

Sen. Susan Collins (R-ME) has said she wants the GOP replacement to insure more people than Obamacare.

Sens. Rob Portman (R-OH), Shelley Moore Capito (R-WV), Cory Gardner (R-CO), and Lisa Murkowski (R-AK) all signed a letter demanding “stability for Medicaid expansion populations.”

Sen. Dean Heller (R-NV) said during a closed meeting with constituents over the weekend that he wanted to push back the Medicaid expansion repeal several more years, according to a Politico report.

Sen. John McCain (R-AZ) told reporters Monday that his constituents were worried about Medicaid cuts.

Perhaps most interesting is Sen. Tom Cotton (R-AR), a staunch conservative who has been vocally criticizing the House GOP’s political strategy as doomed to fail. Cotton just so happens to represent a poor state that has benefited greatly from Obamacare’s subsidies and Medicaid expansion. Cotton told Hugh Hewitt on Tuesday that he thinks the bill will “cost coverage for many Americans, as the CBO said” — and that that’s a problem that needs to be fixed.

You can’t please the Freedom Caucus without infuriating the Coverage Caucus

Here’s the problem for President Trump and Speaker Ryan going forward: The demands of the Freedom Caucus and Coverage Caucus seem to be diametrically opposed.

Many Freedom Caucus members say they view the AHCA’s tax credits for health insurance as a “new entitlement.” They want a less generous bill with less government spending. In particular, they’re reportedly pushing for the Medicaid expansion to be phased out more quickly — beginning in 2018 rather than 2020.

Yet any concession to win Freedom Caucus votes will likely result in a less generous bill that would cause even more people to lose insurance according to CBO projections. And that could drive more wavering members to oppose the bill from the left.

CNN’s Jeremy Diamond explained how this dynamic would work last week, quoting an anonymous House moderate Republican who “immediately said he knew of four other Republicans who would switch from ‘yes’ to ‘no’ if the bill ended the Medicaid expansion in 2017.”

It’s not clear whether the Coverage Caucus or the Freedom Caucus poses a greater threat to the bill’s prospects. Yet it is worth noting that President Trump may have greater leverage over Freedom Caucus members, since most of them come from conservative districts where Trump is very popular. Faced with presidential pressure, it’s possible many of them would agree to go along with an imperfect “repeal-and-replace” plan.

The Coverage Caucus, meanwhile, is primarily concerned about the actual effects repeal would have on millions of Americans. Many of its members are also concerned about losing their seats if they vote for this bill. These are convincing reasons to defy the president and oppose the AHCA. So if President Trump truly does want to sign major health reform legislation, he’d better set about accommodating their concerns.