All that’s left of Adam Wolman’s house is a garden wall. Revisiting his old neighborhood near Los Angeles recently, the creative consultant and former TV executive pulled up to the spot where he lived for over 25 years. The house had just been through a two-year renovation when it burned to the ground in the Palisades Fire in January of last year. Now, it’s an empty lot.

Mr. Wolman’s story is similar to more than 13,000 others’ in Los Angeles County. They include Spencer Pratt, a former reality TV star who has channeled frustrations over the city’s fire prevention and rebuilding efforts, as well as problems like homelessness and drug addiction, into a surging dark-horse campaign for mayor of Los Angeles.

Mr. Pratt’s messaging – around Los Angeles’ decline and the political establishment’s alleged complicity – has been amplified by a series of provocative AI videos circulating on social media. Many of the videos, which are not official products of his campaign (though Mr.…