When Matt Braynard signed on to run Donald Trump’s data team last fall, he got an email from a veteran GOP operative to whom he was close warning, “You realize once you go Trumptard, your career in GOP politics is over?”

Braynard took the job anyway, explaining that he believed in Trump, and that he wasn’t worried about being blacklisted. “This isn’t a career, it’s a vocation, and only God can take that away,” he said he responded.

But according to interviews with more than a dozen operatives — including several who oppose Trump, some who support him and the leaders of some prominent D.C. political shops — some of those who go to work for Trump face an implicit, and occasionally overt, threat: Help Trump, and you’ll never work in this town again.

It may be unenforceable, but the push to stigmatize Trump’s aides, advisers and vendors is among the last remaining pieces of ammunition available to a Republican establishment that has tried just about everything else to block the billionaire from taking over of the GOP. And, critically, it has complicated Trump’s efforts in recent weeks to hire top-tier operatives, according to sources familiar with Trump’s campaign.