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Sen. Ron Johnson on Tuesday questioned whether Sen. John McCain’s brain tumor might have affected his judgment when he voted against a Republican bill to repeal Obamacare.

Johnson, R-Wis., was asked by the hosts of a Chicago radio show why the Senate failed to pass a health care bill last month.

"I'm not gonna speak for John McCain, you know he has a brain tumor right now — that vote occurred at 1:30 in the morning, some of that might have factored in," Johnson said on the "Morning Answer" show.

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Johnson issued a statement several hours later, saying, "I'm disappointed I didn't more eloquently express my sympathy for what Sen. McCain is going through. I have nothing but respect for him and the vote came at the end of a long day for everyone."

The GOP health care bill failed to pass on a vote of 49-51. Three Republican senators — McCain, Susan Collins of Maine and Lisa Murkowski of Alaska — and all Democrats voted against the bill.

McCain, who was diagnosed with brain cancer last month. voted around 1:40 a.m. and there were audible gasps in the chamber when he turned down his thumb to indicate his decision to go against the bill.

Julie Tarallo, a McCain spokeswoman, shot back at Johnson in a statement Wednesday afternoon.

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

Senate Foreign Relations Committee member Sen. Ron Johnson, R-Wis. talks to reporters on Capitol Hill Washington on Aug. 2, 2017. J. Scott Applewhite / AP file

After his crucial health care vote, McCain said he voted against the bill because it should not "rammed through Congress" on a strict-party line basis.

Johnson also said he was frustrated with the way his Republican colleagues handled the repeal effort

"The entire process was awful," he said, "it was a political process and not a problem-solving process."