Former House Speaker Paul Ryan (R-WI) said Monday that President Donald Trump could lose the 2020 presidential election if his “personality” is the central focus of his campaign.

“The person who defines that race is going to win the race. If this is about Donald Trump and his personality, he isn’t going to win it,” Ryan said during a lecture in Vero Beach, Florida, according to TCPalm.com.

The former speaker said President Trump should focus on issues of substance, rather than not style, if he wants to beat his Democrat presidential rival next year. Potential Democrat presidential contenders include Sens. Bernie Sanders (I-VT), Kamala Harris (D-CA), and Cory Booker (D-NJ). Former Vice President Joe Biden and former Rep. Robert Francis “Beto” O’Rourke (D-TX) are expected to launch campaigns in the coming weeks.

Ryan retired from the House in January after serving three years as the chamber’s speaker. Under his watch, Republicans lost a House majority in the 2018 midterm election.

President Trump and Ryan have had an uneasy relationship. In an interview with the Daily Caller, the president blamed Ryan for failing to help secure funding for a U.S.-Mexico border wall.

“Well, I was going to veto the omnibus bill and Paul told me in the strongest of language, ‘Please don’t do that, we’ll get you the wall.’ And I said, ‘I hope you mean that, because I don’t like this bill,'” the president told the outlet.

“Paul told me in the strongest of terms that, ‘Please sign this and if you sign this we will get you that wall.’ Which is desperately needed by our country. Humanitarian crisis, trafficking, drugs, you know, everything — people, criminals, gangs, so, you know, we need the wall,” he added. “And then he went lame duck.”

Breitbart News published October 2016 audio of Ryan vowing to never defend President Trump following the release of the Access Hollywood tape. “His comments are not anywhere in keeping with our party’s principles and values,” Ryan said. “There are basically two things that I want to make really clear, as for myself as your Speaker. I am not going to defend Donald Trump—not now, not in the future. As you probably heard, I disinvited him from my first congressional district GOP event this weekend—a thing I do every year. And I’m not going to be campaigning with him over the next 30 days,” Ryan said during a conference call with Republican lawmakers.

Ryan was the vice presidential candidate for Sen. Mitt Romney’s (R-UT) failed 2012 White House bid.