Fred Malek, finance chairman of the Republican Governors Association, said that wealthy donors are simply “more hesitant to put large sums to work until they see more results.”

“I think donors are going to take a very hard look at that before they put in large money between Indiana and California,” Malek said.

Erickson’s ad hoc coalition of anti-Trump Republicans, for instance, is planning a conference call on Wednesday to discuss its next steps, including reexamining a third-party challenge.

“You’re already starting to see two tracks moving forward,” Erickson said, adding that a Trump win Tuesday would mean “much more energy going toward a third-party candidate.”