Fox News has canceled “Lou Dobbs Tonight,” the program hosted by television’s staunchest supporter of Donald Trump and of his assertions of voter fraud in the 2020 election, The Times has learned. Dobbs’ program, which airs twice nightly at 5 and 7 p.m. Eastern on the Fox Business Network, will have its final airing Friday, according to a Fox News representative who confirmed the cancellation. Starting next week, the program will be called “Fox Business Tonight,” with rotating substitute hosts Jackie DeAngelis and David Asman, who filled in for Dobbs on Friday.