Mr. McConnell may have been betting that pressure from a majority of Republicans — who have been promising for the better part of a decade to unravel President Barack Obama’s signature domestic policy achievement — would get senators from Medicaid expansion states on board to do just that.

But the forces arrayed against Mr. McConnell were many, including doctors and hospitals, patient advocacy groups and, perhaps more than anyone else, governors — many of them Republicans — from states where tens of thousands of residents have found themselves newly insured under the health care law and are not eager to see that evaporate.

“There may be some philosophical, you know, kind of textbook disagreement,” Gov. John R. Kasich, Republican of Ohio, said at a news conference in Washington on Tuesday. “But when you sit in a room and you say to people, ‘Should we strip coverage from somebody who’s mentally ill?’ I’ve never heard anybody say yes.”

Last week, Senator Dean Heller, Republican of Nevada, stood at a news conference with Brian Sandoval, the state’s extremely popular Republican governor, and said that the “bill that’s currently in front of the United States Senate is not the answer — it’s simply not the answer.”

Mr. Heller added, “It’s going to be very difficult to get me to a yes.”

Mr. Heller gave voice — an early and deeply unappreciated one, it seems, from Mr. McConnell’s perspective — to a number of senators from across the spectrum who were feeling pressure from their governors, and in some cases state insurance officials, to resist any bill that was going to raise premiums, increase the number of uninsured or anything else that officials there disliked.

Then there is the not-so-small matter of President Trump, who in any other universe would be the greatest asset Mr. McConnell could have, but has turned out to be quite the opposite. Republican senators all watched carefully as Mr. Trump at times berated, cajoled and mildly wooed House Republicans, who had their own divisions, to get to yes on their version of a health care bill.