text:  This interview went to the heart of Biden's biggest Achilles heel, whether he's still up for the job at 81. ABC News anchor George Stephanopoulos addressed this head on. He focused on Biden's physical and mental ability to do the job and run again. He asked whether Biden would be willing to have a cognitive test, and Biden said he didn't need it. And Biden says he's confident he's more popular than the polls make it seem. Listen to this exchange about it.