John McCain. AP

On Thursday, Sen. Lindsey Graham made a demand: He would vote for the terrible healthcare bill being offered before the Senate, a bill he thought would cause health-insurance market disaster if enacted, as long as he received clear assurances that the House would never send it to the president to make it law.

This was weird — as was the fact that Graham ultimately got what he apparently saw as sufficient assurance and voted for the bill. But like a lot of the weird things Republicans have said and done on healthcare in the past few months, it makes sense if you understand their underlying political goals.

All the options Republicans have left themselves on healthcare are both terrible policy and dreadfully unpopular. So members haven't set out to make good policy. They have set out to avoid being blamed for whatever becomes law — and also to avoid being blamed if nothing becomes law.

Lots of Republicans want Trumpcare to die, but nobody wants to be the Republican who murdered it.

Except John McCain.

Early Friday morning, McCain arranged to vote out of alphabetical order so he could provide the "no" that killed the bill to the applause of his Democratic colleagues. He built up as much drama as he could for the moment, telling reporters who asked about his intentions before the vote that they would have to "watch the show." Democratic Sen. Dianne Feinstein hugged him on the Senate floor.

If you've been asking why McCain is getting so much credit for this hit job, rather than his two female Republican colleagues without whose "no" votes the bill would have also passed, one of the answers is that he has sought to make himself the fall guy.

But it's true: This was a conspiracy of three. And one thing McCain has in common with Sens. Susan Collins and Lisa Murkowski is that all three were in an unusually good position to take the blame for killing Obamacare.

Collins represents a state, Maine, that voted for Hillary Clinton. Unlike every other Republican who remains in the Senate, she voted against the 2015 bill to repeal most of Obamacare that President Barack Obama vetoed — no hypocrisy here.

Collins is rumored to want to run for governor of Maine. As long as Obamacare stays the law, there will be a pot of Medicaid expansion funds waiting for the state to unlock, creating a windfall into the state budget Collins would oversee.

Murkowski, of Alaska, is one of the few senators who answer to a truly moderate voter base. She won reelection in 2016 with 44% of the vote, against 29% for a candidate to her right and 25% for two candidates to her left. She's already shown, in 2010, that she can lose a Republican primary and come back to win the general election as a write-in.

When the ice-bucket challenge was a thing, Murkowski jumped into below-freezing Alaskan ocean water instead of just taking a bucket of water to the head. She's not afraid of Interior Secretary Ryan Zinke.

And McCain? Well, how do you threaten an 80-year-old man who is facing down an aggressive form of brain cancer? By threatening to back his primary challenger in 2022?

One piece of conventional wisdom in the months of debate over healthcare had been that any bill would either pass by a single vote or fail by many. Friday morning's 49-to-51 defeat proved that wrong — and if you think about it, you can understand why it's wrong.

On Thursday afternoon, McCain held that press conference with Graham and Sen. Ron Johnson — the one in which Graham called the bill "terrible policy" that he'd vote for only if House Speaker Paul Ryan swore up and down that it would never become law.

Hours later, when Graham announced that he'd been sufficiently assured, most of us assumed his close friend and ally McCain would go along too. If McCain was going to make a stand, why wouldn't Graham stand along with him?

I wonder whether McCain and Graham had a true break on the issue or whether they realized only one of their votes would be needed to kill Trumpcare, so Graham could be a "good soldier" and vote for the bill with confidence it wouldn't even get out of the Senate.

Maybe the bill needed to fail by a one-vote margin, so the maximum number of Republicans could say they tried their hardest to repeal Obamacare and would have succeeded if old John McCain hadn't stood in the way.

A lot of Republicans are mad at John McCain for killing (this incarnation of) the repeal. But in time, they will be glad for the political cover he gave them by taking the fall for a murder many of them wanted to commit, so the party would not have to take ownership of an electorally disastrous policy.