The Republican Party has a historic opportunity to revive the old Reagan coalition. The person standing in the way is the 45th president, writes the former attorney general.During the Republican primaries in 2016, I supported, in succession, every alternative to Donald Trump. I did not see him as our party’s standard-bearer. He was not my idea of a president. I could see that he was grossly self-centered, lacked self-control, and almost always took his natural pugnacity too far. While he could be compelling, I found myself cringing at his frequently juvenile, bombastic, and petulant style.I also saw Trump’s strengths. I...