A spokesman for Sen. John McCainJohn Sidney McCainGOP strategist donates to Alabama Democrat Meghan McCain knocks Bannon: 'Who the hell are you' to criticize Romney? Dems demand Tillerson end State hiring freeze, consult with Congress MORE (R-Ariz.) is criticizing Sen. Ron JohnsonRonald (Ron) Harold JohnsonOvernight Cybersecurity: Panel pushes agencies on dropping Kaspersky software | NC county won't pay ransom to hackers | Lawmakers sound alarm over ISIS 'cyber caliphate' GOP chairman warns of ISIS's ‘cyber caliphate’ Overnight Finance: House approves motion to go to tax conference — with drama | GOP leaders to consider Dec. 30 spending bill | Justices skeptical of ban on sports betting | Mulvaney won't fire official who sued him MORE's (R-Wis.) remarks suggesting McCain's brain cancer might have been a factor in his vote against ObamaCare repeal.

"It is bizarre and deeply unfortunate that Sen. Johnson would question the judgement of a colleague and friend," a McCain spokesman told NBC.

"Senator McCain has been very open and clear about the reasons for his vote," said the spokesman, who was not identified by name in the NBC report.

McCain was one of three Republican senators to buck their party in voting against the Senate GOP's scaled-down ObamaCare repeal bill.

Johnson earlier on Wednesday told a Chicago radio station that the late hour of the vote and McCain's tumor might have "factored in" to his decision.

“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.