“We’ve got to clearly show that we reject socialism,” Hickenlooper said. “We’ve got to do that because Republicans will try to make us into socialists even if we’re not. If we’re not willing to draw a bright line and say we’re not socialists, we could quite possibly reelect this president.”

Some in the audience disagreed with Hickenlooper’s thinking. Jonathan Tasini, a labor activist who endorsed Sanders in 2016 and published a book about the senator’s ideas, said that Hickenlooper had effectively talked his way out of the 2020 race. Hickenlooper had also been booed for saying that Democrats should not “[remove] private insurance from over a hundred million Americans,” a reference to Medicare-for-all legislation.

“Every single presidential candidate who came into this hall was treated with respect,” Tasini said. “He red-baited us and got down in the mud, and I think it finished him.”

Hickenlooper’s allies saw it differently, speculating that the cold reception at a convention dominated by liberal activists would help distinguish the governor to moderate Democratic voters. Asked how the booing might play on Fox News, which has devoted hours of coverage to the rise of socialists inside the party, Hickenlooper said it would help.