WASHINGTON (AP) — Joe Biden faced a test Thursday that he had avoided so far this year — a solo news conference with questions from the White House press corps. He made at least two notable flubs, referring at an event beforehand to Ukrainian President Volodymyr Zelenskyy as “President Putin” and then calling Kamala Harris “Vice President Trump” when asked about her by a reporter. But he also gave detailed responses about his work to preserve NATO and his plans for a second term. And he insisted he’s not leaving the race even as a growing number of Democratic lawmakers ask him to step aside.