In taking reporters’ questions for almost an hour at Thursday’s news conference after the NATO summit in D.C., President Biden showcased his foreign policy prowess but also the gaffes that sparked concern from Democratic officials, voters and donors about his fitness to continue his reelection campaign. Biden mistakenly referred to Vice President Harris as “Vice President Trump” in the session’s opening minutes and stumbled over words and phrases several other times. The Biden campaign hoped the performance would stem the tide of calls for him to step aside, but three more House Democrats called for him to leave the ticket in the hours afterward, bringing the total to 20.