Hillary Clinton's campaign got spooked when Donald Trump's candidacy took off, even though Democrats were cheering the billionaire developer's rise, says Jennifer Palmieri, who worked as Clinton's communications director.

"Here's the thing about running against Trump is he was just going to be unconventional," Palmieri said on HuffPost's weekly podcast "Candidate Confessional."

"Hillary Clinton is a conventional candidate. So I was concerned about how that plays out. My most sleepless nights, my most anxiety-ridden time was February, March, April and trying to like wrap your head around how you're going to run against Donald Trump.

"It seemed like there could be a big payoff, but I would prefer something a little more conventional … [Trump] was Teflon, because he lives by his own set of rules, so gravity doesn't apply to him."

She further worried when she saw GOP presidential candidate Jeb Bush, the former Florida governor, being hammered by Trump.

"It was really scary watching what happened to Jeb [Bush]," she tells the podcast. "I thought, you know, that's us," Palmieri said.