Republican governors can make or break congressional Republicans' latest attempt to repeal Obamacare. And on Tuesday, a bipartisan group of 10 governors may have just seriously damaged a repeal bill's prospects.

The governors, five of them Republican or Republican-leaning, sent a letter to congressional leaders urging them not to support repeal legislation championed by GOP Sens. Lindsey O. Graham (S.C.) and Bill Cassidy (La.). At least three other GOP governors who didn't sign the letter are opposed to the repeal bill, while 15 other governors GOP governors wrote a letter endorsing the plan.

Even though the bill dismantles Obamacare and gives states near-universal power to set up health insurance programs, it doesn't hand the states much money to do that.

“We ask you to support bipartisan efforts to bring stability and affordability to our insurance markets,” the opposition letter says, referring to bipartisan talks in the Senate to stabilize, not erase, key parts of Obamacare.

Republican governors were major pressure points this summer for GOP lawmakers on the fence about an earlier bill that cut Medicaid funding by much less. There's evidence to suggest the pressure worked: Of the 13 GOP senators who had concerns about or didn't support the July version of the legislation, eight of their states' governors also didn't support it.


Sen. Lindsey O. Graham (S.C.) listens as Sen. Bill Cassidy (La.) speaks to the media Tuesday. The two Republicans are sponsoring a new health-care bill. (Andrew Harrer/Bloomberg News)

Republican senators wobbling on this repeal bill will almost certainly take into account how their state's governor feels about it, since governors are the ones who would have to implement it. This proposal in particular relies on states to do the heavy lifting of insuring people. 

And that's why this letter is so damaging for the Graham-Cassidy legislation. The 10 governors who signed it head states represented by nine GOP senators.

At least one of those senators is a critical swing vote. Sen. Lisa Murkowski (Alaska) voted against a repeal bill in July, and her state's governor, Bill Walker (I), signed the letter opposing this version, too. On Tuesday, before this letter arrived, Murkowski told reporters she wants to see how much funding Alaska and other states would get before making a decision.

One additional “no” vote might be enough to sink this legislation. Senate Republicans can only afford two "no" votes from their party, and they already have one firm "no" and one likely "no”: Sens. Rand Paul (Ky.) and Susan Collins (Maine).

Of course, senators aren't required to listen to their governors. Sen. John McCain (R-Ariz.) cast a surprise “no” vote in July even though his governor had supported that legislation.

The opposite dynamic is playing out now between Nevada's GOP senator and GOP governor. Sen. Dean Heller supports this legislation even though he opposed a lighter version of Obamacare repeal this summer because his governor didn't like it.

Now Heller is a sponsor of the Graham-Cassidy bill, and Nevada Gov. Brian Sandoval (R) is urging leaders not to take it up.

Governors won't sink an Obamacare repeal on their own. They can't vote in Congress, after all. But a notable number of governors can — and are — exerting a whole lot of influence on Republican senators to vote against this bill. If they change the course of just one or two senators, they will have killed Republicans' last, best chance to repeal Obamacare.