He is wearing aviators and baseball caps. He is making visits to ice cream parlors and barbecue joints, and asking to meet with influencers who can disseminate images of him on TikTok and Instagram. He is talking more often to reporters and fielding questions on the Middle East, Republicans and, of course, his age.None of this is a coincidence. As President Biden faces what polls show is significant concern about his 81 years, and a tight election against his likely opponent, Donald J. Trump, the White House strategy is to have him step out of his protective bubble and directly take on…