text:  These interviews, as well as a press conference last week, are at least partially about proving he has what it takes after a very bad debate. The idea that I'm the old guy. I am. I'm old. But I'm only three years older than Trump, number one. And number two, my mental acuity has been pretty damn good. Biden then touted his record in office. Tamara Keith, NPR News. On Wall Street and pre-market trading, Dow futures are higher. It's NPR.