The situation has left Trump feeling “nervous about Oz’s prospects,” according to one Trump adviser, who requested anonymity for fear of reprisal.

“For the past five months, he’s been told the only threat to Oz is named David McCormick. This is a twist no one saw coming,” the adviser said.

Another person close to Trump who has been supportive of Oz described the situation as “a nightmare.” In interviews with CNN, this person and three other Trump allies described Barnette, who nabbed endorsements late Tuesday from the socially conservative groups Susan B. Anthony List and CatholicVote and a seven-figure investment from the Club for Growth, as a major threat to both Oz and McCormick in the last stretch of the race…

The former President is still determining whether there is anything he can do to give Oz an extra boost in the race, the adviser to Trump said, noting that Trump was already planning to host a tele-rally and to target Republican voters with robocalls before the primary. Trump also held a campaign rally outside of Pittsburgh last Friday, where he repeatedly tore into McCormick to turn on-the-fence voters against him.