Former Colorado governor John Hickenlooper found a way to stand out at a crowded gathering of California Democrats: He denounced “socialism,” and got booed.

“If we want to beat Donald Trump and achieve big progressive goals, socialism is not the answer,” Hickenlooper said at a Saturday afternoon session of the state party’s annual convention. As the jeering grew louder, Hickenlooper added: “You know, if we’re not careful, we’re going to end up reelecting the worst president in American history.”

Hickenlooper’s presidential campaign had previewed the remarks hours before he spoke. The Coloradan, who was a geologist and a brewer before entering politics, has repeatedly argued for Democrats to embrace and reform capitalism.