Ivanka Trump had been a mentor and judge on the NBC's "Celebrity Apprentice" show.

The National Prayer Breakfast is an annual rite where presidents celebrate faith and fellowship - or, in President Donald 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 a recent interview with our Washington Post colleague Karen Tumulty), it's actually not so surprising.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 possibility for Trump's "Rosebud" moment: 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.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.