Sen. Ron Johnson, R-Wis., suggested Tuesday Sen. John McCain's brain tumor, coupled with the timing of the healthcare vote in the Senate, may have played a role in McCain's vote against the bill to repeal provisions of Obamacare.

"I'm not going to 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," Johnson told the radio show "Chicago's Morning Answer."

The radio host pressed Johnson on whether he really felt McCain's brain tumor impacted his judgment.

"Again, I don't know exactly — we really thought — and again I don't want to speak for any senator," the Wisconsin Republican said. "I really thought John was going to vote yes to send that to conference at 10:30 at night. By about 1, 1:30, he voted no. So you have to talk to John in terms of what was on his mind."

Julie Tarallo, spokeswoman for McCain, said in a statement Johnson's comments were odd given the Arizona senator's explanations of his vote.

"It is bizarre and deeply unfortunate that Senator Johnson would question the judgment of a colleague and friend," Tarallo said. "Senator McCain has been very open and clear about the reasons for his vote."

McCain flew back to Washington, D.C. to vote on the healthcare bill days after he had surgery to remove a blood clot above his left eye, which led to a brain cancer diagnosis.

The Arizona Republican ended up surprising many Republicans when he, along with GOP Sens. Susan Collins of Maine and Lisa Murkowski of Alaska, voted against a "skinny" repeal bill in the early morning hours.

The trio's "no" votes ended up effectively killing the Senate's efforts to repeal and replace Obamacare before they left for the month-long August recess, though some lawmakers and the White House are urging the Senate to go back to the drawing board.

McCain said last week he was opposed to the process that led up to the vote on the "skinny repeal" bill, though some senators like Johnson said they backed the proposal because it would've led them to conference with the House.

"We did get a call from [House Speaker] Paul [Ryan] and he assured us that skinny repeal was not going to pass the House. It would have to go to conference," Johnson said Wednesday.