MILWAUKEE (AP) — Donald Trump’s running mate JD Vance will introduce himself to a national audience as he addresses the Republican National Convention. The Ohio senator’s headlining address on Wednesday will be his first speech as the Republican vice-presidential nominee. He’s a relative political unknown who rapidly morphed in recent years from a severe critic to an aggressive defender of Trump. Vance is the first millennial to join a major-party ticket, and he joins the race as questions about the age of the men at the top of the tickets — 78-year-old Trump and 81-year-old President Joe Biden — have been high on the list of voters’ concerns.