COLUMBUS, Ohio — President Trump said Friday night that Republicans will prevail in the midterm elections because Democrats “are not in a position to govern” with lax immigration policies that he said led to the death of Iowa teenager Mollie Tibbetts and others. Speaking to the Ohio state Republican Party’s annual dinner, Mr. Trump predicted, “This November we are going to win really big.” “Today’s Democrats are not just extreme, they are really not in a position to govern,” he said. “They are just not in a position to govern when you look at what they are for — open...