Transportation Secretary Pete Buttigieg said former President Donald Trump is a “master” at turning any television event into a show about himself and warned that Vice President Kamala Harris has a challenging task ahead at the presidential debate.

“I’ve competed with her for the Democratic nomination, and I had the honor of being involved in her debate preparations against Mike Pence,” the 2020 presidential candidate said on CNN’s “State of the Union” on Sunday. “She is a very focused and disciplined leader, but it will take almost superhuman focus and discipline to deal with Donald Trump in a debate.”

“It’s no ordinary proposition, not because Donald Trump is a master of explaining policy ideas and how they’re going to make people better off. It’s because he’s a master of taking any form or format that is on television and turning it into a show that is all about him,” he continued.

He said it was important for the vice president to keep the focus on her agenda, ensuring Americans understand how different her vision is from Trump’s.

“It’s, again, an extremely challenging task in the face of all of the distraction, whatever outrageous things he does and says, because they will require a response, and yet you can’t allow him to change the subject from the difference between his very unpopular set of policies and record and her vision for Americans’ future,” the transportation secretary said.

Harris and the former president will face off Tuesday night in Philadelphia for what may be their only debate before the November election.

It will be moderated by ABC News and begins at 9 p.m. Eastern time.