Warren Buffett made clear he would not publicly back either Kamala Harris or Donald Trump in the race for the White House. His nearly trillion-dollar conglomerate, Berkshire Hathaway, issued a statement on social media warning of “fraudulent” endorsements.

That theory is based on moves Buffett made in recent months to unload an array of stocks that have significantly appreciated since he purchased them. Those include hundreds of billions of dollars in Apple and Bank of America shares that he’s sold over ...