“When you attack him,” Melania Trump said of her husband on the campaign trail last year, “he will punch back 10 times harder.”

But it is unclear how effective this approach will be with Freedom Caucus members, some of whom might become even more entrenched in response to Trump’s attacks.

“Goading the Freedom Caucus to get on board through social media, how effective that will be, I don’t know. It doesn’t affect me,” said Rep. Jeff Duncan, one member of the group. “…Some may blow up even more, because that’s just how they roll. I see it for what it is: a tool being used by President Trump to influence the activities in Congress.”

But Twitter is not the sole tool at Trump’s disposal, and there is some speculation that he will supplement his tweets with a true political blitz — including advertising and campaign-like swings through members’ districts. He reportedly threatened as much when the health-care push sputtered, sending Mulvaney to tell Rep. Mark Sanford: “‘The president asked me to look you square in the eyes and to say that he hoped that you voted ‘no’ on this bill so he could run [a primary challenger] against you in 2018,'” Sanford told the Post and Courier.