Michelle Cottle: “If Mr. Ossoff winds up in the White House, Mr. Trump will have largely himself to blame. The president didn’t just help him win his seat. He also spent years undermining the Republican Party in Georgia, sowing internecine discord, championing losing candidates and destroying conservative voters’ faith in the electoral system.”“With impressive, if unintentional, drive, Mr. Trump has fostered the conditions that transformed Mr. Ossoff from a charmingly nerdy, vaguely awkward, low-key freshman lawmaker into a political star.”