Trump over the weekend threatened to prosecute donors, lawyers and elections officials who he claimed “cheated” in the 2020 election or who engaged in behavior he deemed “unscrupulous” in November. And he elevated a dubious claim about fraud involving mail-in ballots in Pennsylvania, echoing rhetoric he used to cast doubt on the 2020 results. Republicans have long argued Trump’s fixation on the 2020 election and his claims of widespread fraud are unhelpful politically, but critics viewed Trump’s most recent posts as a blaring warning sign about how Trump may react to November’s results, win or lose. “As we head into...