Mr. Trump sent an email via his assistant to Jeffrey A. Rosen, the incoming acting attorney general, that contained documents purporting to show evidence of election fraud in northern Michigan — the same claims that a federal judge had thrown out a week earlier in a lawsuit filed by one of Mr. Trump’s personal lawyers. Another email from Mr. Trump to Mr. Rosen followed two weeks later, again via the president’s assistant, that included a draft of a brief that Mr. Trump wanted the Justice Department to file to the Supreme Court. It argued, among other things, that state officials had used the pandemic to weaken election security and pave the way for widespread election fraud... On the day that Mr. Trump announced that Mr. Rosen would be the acting attorney general, he wanted him to look at materials about potential fraud in northern Michigan, according to an email obtained by the committee. That fraud claim had been the subject of a lawsuit filed by the former Trump adviser Sidney Powell, who argued that Dominion voting machines had flipped votes from Mr. Trump to Joseph R. Biden Jr.