Arizona Sen. Jeff Flake, who has long avoided endorsing GOP nominee Donald Trump, said Sunday that at this rate it’s unlikely he will be able to back him before Election Day.

“It becomes increasingly difficult to see that he’s going to change, so I don’t expect that I’ll be able to support him in November,” Flake told CBS’ “Face the Nation.” “I’d like to, he’s the Republican nominee, I just don’t see how I can.”

He criticized Trump for what he called the candidate’s “360-degree pivot” on immigration in the last few weeks, adding that his “confusing” position on the issue is problematic.

“Some people, as he said, said it was hardening, some said softening, I say it was just confusing,” Flake said. “With regard to immigration he pivots and then pivots right back — so it’s kind of a 360-degree pivot at times.”

The first-term Arizona senator said there are four key elements to an immigration plan: border security, enforcement within the U.S., a temporary worker program and a “mechanism” for dealing with people who are already in the country illegally. Trump has addressed the border security aspect with his proposed wall along the U.S.-Mexico border, Flake said, but he’s barely touched on some of the other components of an immigration policy.

Flake said he was initially encouraged by Trump’s surprise trip to Mexico to meet with Mexican President Enrique Pena Nieto, but that Trump’s hard-line speech on immigration that night made it clear no real change was coming.

“The speech in Mexico and that action, I think all of us had some hope after that that he might be changing the tone and tenor of his campaign,” Flake said. “But then when the speech was delivered in Arizona later that day, he seemed to be right back where he has been.”

Flake praised the moves of his fellow Arizona Sen. John McCain in distancing himself from Trump in his own Senate reelection race. After winning his Republican primary last week, McCain released a video saying he would be a “check” on a Hillary Clinton administration.

“He’s doing what I think Republicans need to do,” Flake said. “If we want the future of our party to be what it needs to be, we can’t associate with this kind of message and certainly with this kind of tone and the rhetoric that’s being used. Long-term I think that drives away young voters, it certainly drives away a lot of people in the minority community that we’re going to need moving ahead.”

As for his home state of Arizona, where the Clinton campaign is putting more resources for the final two months of the campaign, Flake said he thinks the usually-red state is actually in play this fall.

“It shouldn’t be up for grabs—Mitt Romney won it by I think eight points—but frankly it is,” he said. “And I think that they’re spending money because they have some indication that she might be in play. And unfortunately I think that’s the case.”