“There are a number of people, plenty of whom we don’t even know about yet, who are torn” about running again, said one national GOP strategist involved in House races. “Whether there’s measurable progress on tax reform the next 30 days will be determinative. If we get to November 1st and it looks like tax reform isn’t happening, I think there’ll be a mass exodus.”

“It’s a disaster if it doesn’t happen,” conservative Rep. Trent Franks (R-AZ) warned, referring to a failure to make meaningful progress on tax reform. “That has an effect. People like me who are here for the cause, if we see no hope for the cause, which in my case will never happen, that would have a terribly damning effect on our stamina here.”

Other conservatives offer similar warnings.