Senators Lindsey Graham, John McCain, and Ron Johnson. Photo: Justin Sullivan/Getty Images

When Senator John McCain returned to Washington last month, less than two weeks after surgery to remove a blood clot from his brain, and cast the deciding vote against the Senate’s “skinny repeal” of Obamacare, it was reasonable to wonder if the decision was driven at all by his recent cancer diagnosis.

After all, what better reminder of the importance of health-care access than the surprise discovery of a brain tumor?

Though McCain’s explanation for his vote did not mention his diagnosis, one of his GOP colleagues believes that the tumor did in fact affect the Arizona senator’s vote, but not for the reason stated above.

“Again, I’m not gonna speak for John McCain — he has a brain tumor right now — that vote occurred at 1:30 in the morning, some of that might have factored in,” Senator Ron Johnson of Wisconsin said on AM560 “Chicago’s Morning Answer.” First reported by CNN, Johnson’s comments came after explaining that House Speaker Paul Ryan had promised that the “skinny repeal” would go to conference, an assurance that would presumably have had McCain voting “yes.”

Asked if the tumor “really” had McCain confused, as he seemed to imply, Johnson didn’t back away. “I really thought he was going to vote yes to send that to conference at 10:30 at night,” he said. “By about 1, 1:30, he voted no. So you have talk to John in terms [of] what was on his mind.”

Responding to Johnson’s suggestion, a spokesperson for McCain said, “It is bizarre and deeply unfortunate that Senator Johnson would question the judgment of a colleague and friend.”

So yes, you could believe that McCain accidentally voted yes because his brain was addled by the lateness of the hour. Or you could listen to McCain’s own explanation. He sounds a lot less confused about his vote than Johnson.