"That’s a possibility," he told ABC's Jon Karl and Rick Klein during an interview on their podcast "Powerhouse Politics." Arizona voters can write McMullin in on their ballot.
Flake, among a handful of Senate Republicans who have never supported Trump, says his popularity has dropped at home because of it, and that he’s relieved he’s not up for re-election until 2018, by which time he hopes tempers will have subsided.
“I won’t lie, it’s not been easy,” he said, going on to paraphrase a John McCain joke that Congress’ popularity is down to paid staffers and blood relatives.
“I always thought I was fine having 10 siblings and 69 first cousins on my father’s side. I’m not sure that blood relatives, they hold anymore,” he joked.
Despite polls showing tightening margin's between Clinton and Trump in many battleground states, Flake said he was skeptical that the outcome of the race, which he said Trump will be "very unlikely" to win, will be close.
Flake, a member of the Senate Judiciary Committee, also reiterated his belief that Supreme Court nominee Merrick Garland should get a confirmation hearing in the post-election, pre-inauguration lame duck session.
"Hillary Clinton will not likely nominate somebody as conservative as Garland. I’m not suggesting he’s that conservative, he’s just more conservative than somebody she would name, particularly if she has a Democrat Senate," he said.
Given his post on that influential committee, Flake has also interacted routinely with FBI Director James Comey. He said he was surprised when Comey made such a public show in July of criticizing Hillary Clinton's email practices while also declining to indict her, so he wasn't as surprised when Comey, upon acquiring potentially relevant, new information in the case, again went public with it.
Clinton has said there is "no case" regarding the review of the newly discovered emails on longtime aide Huma Abedin's computer.
The junior Arizona senator refused to game out the fate of Senate control post-Election Day, but he did say he believes it's "very, very close and I wouldn't want to call it today."
He also avoided speculating about whether current Majority Leader Mitch McConnell, who has drawn the ire of some conservatives who accuse him of being a member of the “Washington establishment,” would be able to retain his post as Republican Leader if Democrats regain the majority.
"I wouldn't want to speculate losing the Senate. I'm still hopeful we'll hold it,” he said.