In a turn of events that shocked the political world and threw the presidential race into unprecedented turmoil, Donald J. Trump announced yesterday that he is quitting the race and endorsing Hillary Clinton. Trump said the only point of his campaign was to show how stupid and gullible many Republican voters are. “I’ve been a Democrat all of my adult life,” Trump told a packed and boisterous news conference. “But I knew if I ran as a Republican and said increasingly ridiculous, idiotic, racist and sexist things that I would get a lot of votes.” But he said he had no idea he would be able to win the Republican nomination and poll 40 percent or better in a national race against Clinton. “Did people ...