 Former President Donald Trump is nominated by delegates at the Republican National Convention. He has chosen Senator J.D. Vance of Ohio as his running mate. Vance is a millennial. He'll turn 40 in just a few weeks. A memoir author and a one-time fierce Trump critic turned MAGA supporter. ABC's Jay O'Brien is on the floor of the Republican National Convention in Milwaukee where the Veep Stakes winner was well-received.