Donald Trump to Meet With Senator Joni Ernst, a Possible Running Mate By MAGGIE HABERMAN Donald J. Trump said on Twitter on Monday that he would meet in New Jersey with Senator Joni Ernst, Republican of Iowa, as he screens potential running mates in a series of meetings. One person briefed on the process, who was not authorized to speak publicly, said that the campaign began vetting Ms. Ernst in recent days as a possible vice-presidential pick. Jason Miller, a senior communications adviser for Mr. Trump, declined to comment. A spokesman for Ms. Ernst could not be reached. Ms. Ernst...