What’s behind the feud between former California governor Arnold Schwarzenegger and President Trump? (Thomas Samson/AFP/Getty Images; Paul J. Richards/AFP/Getty Images)

The National Prayer Breakfast is an annual rite where presidents celebrate faith and fellowship — or, in President Trump’s case, mock Arnold Schwarzenegger, the man who succeeded him as the host of NBC’s “Celebrity Apprentice.”

“The ratings went right down the tube,” Trump said, describing what happened after he left the show in 2015 and was replaced by the movie-star-turned-politician. “I want to just pray for Arnold for those ratings.”

Trump’s trolling of Schwarzenegger from the dais of the religious event should seem remarkable. But given the president’s repeated, typically unsolicited, mention of the former California governor’s relatively low ratings (unprompted, he brought Schwarzenegger up three times in this interview with our colleague Karen Tumulty), it’s actually not so surprising. Which is, in the president’s own parlance, “sad!”

So what’s behind this seeming fixation? Why does the leader of the free world care so much about a guy who starred in “Kindergarten Cop?” Here’s one “Rosebud”-like possibility for Trump’s obsession: Trump badly wanted his daughter, Ivanka, to take over the job hosting “Celebrity Apprentice” after NBC severed ties with him following his campaign-trail comments about Mexican immigrants, according to one person who spoke to the president about the matter.

President Trump asked for prayers for Arnold Schwarzenegger, his successor on "The Apprentice," at National Prayer Breakfast on Feb. 2 in Washington. (The Washington Post)

Ivanka Trump, along with her brothers Eric and Donald Jr., had been mentors and judges on the show. Trump thought Ivanka would be the ideal candidate, according to the person who talked to Trump about it. Telegenic and poised, Ivanka Trump, who until recently was the executive vice president of the Trump Organization, has frequently been the public face of the family brand.

It may be that Trump never got over the network’s decision to go with another host — and seems to be taking it out on their choice.

Of course, there are other reasons for keeping alive the beef with Schwarzenegger: It’s a chance for him to remind people about his own (higher) ratings. And he remains an executive producer of the show, an arrangement that could mean he is still drawing a paycheck whose size would depend on the show’s success.