Senate Republican Ron Johnson of Wisconsin suggested in a radio interview that colleague John McCain’s cancer and the very late hour might have played a role in McCain's dramatic and decisive vote last month against a GOP bill to roll back Obamacare.

Johnson was asked on “Chicago’s Morning Answer” Tuesday about the vote McCain took that effectively ended a Republican push this summer to repeal Obamacare.

“I am not going to 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 AM-560 in Chicago in comments first reported Wednesday by CNN.

“Really?” asked co-host Amy Jacobson, referring to McCain’s surgery for a blood clot and subsequent flight to Washington for the late July Senate health care debate. It was McCain's surgery that revealed the presence of brain cancer.

“You really think that that played a factor in his judgment call?" she asked Johnson.

“Again, I don’t know exactly what — we really thought that — again I don’t want to speak for any senator,” Johnson said. “I really thought John was going to vote yes to send that to conference at 10:30 at night. By about 1 or 1:30 (in the morning), he voted no. You’d really have to talk to John about what was on his mind.”

McCain spokeswoman Julie Tarallo responded Wednesday:

“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.”

Johnson issued a statement of his own Wednesday afternoon expressing regret over his comments about McCain's vote:

"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."

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Johnson had joined fellow Republicans McCain and Lindsey Graham of South Carolina at a news conference late in the debate to discuss the so-called skinny repeal, which represented the GOP leadership's last attempt to get an Obamacare repeal bill through the Senate,

The bill was not presented to Republicans as a solution, but simply a vehicle to get to a conference with the House GOP to negotiate a final health care measure. Johnson, McCain and Graham asked for assurances from House Speaker Paul Ryan that the House would not simply vote to pass the skinny repeal bill, and Ryan promised to hold a conference to work out a new bill.

Graham and Johnson subsequently voted yes on the bill, but McCain said Ryan's comments offered no guarantees that skinny repeal would not be passed by the House at some future date.

Taking questions on a Facebook Live appearance Wednesday, McCain reiterated his concerns about the health care bill he voted against:

“Let’s go through the normal legislative process ... not having something done behind closed doors by quote skinny repeal – what does skinny repeal mean, by the way?” said McCain, who argued that whatever came out of a conference with the House would leave senators with only a "yes" or "no" choice to accept the negotiated bill.

He said he voted no in the hopes of bringing new legislation back through committee and the regular lawmaking process.

McCain also said of his own health: “My treatment is going fine, (I’m) feeling fine. This is a rough disease, let’s be very honest ... I have to beat it.”

The senator added:

“To my Democrat friends and some of my Republican friends, I’m coming back.”