Former President Donald Trump chose Sen. JD Vance of Ohio as his running mate on Monday, picking a onetime critic who became a loyal ally and is now the first millennial to join a major-party ticket at a time of deep concern about the advanced age of America’s political leaders.

“After lengthy deliberation and thought, and considering the tremendous talents of many others, I have decided that the person best suited to assume the position of Vice President of the United States is Senator J.D. Vance of the Great State of Ohio,” Trump said in a post on his Truth Social network as the Republican National Convention got underway in Milwaukee.