Former Presidents Joe Biden, Barack Obama, George W. Bush and Bill Clinton are sharing a message of optimism with Americans as the nation approaches its 250th anniversary. The four presidents each spoke individually with Jenna Bush Hager in a "TODAY" exclusive on April 21 in which they expressed their hope for the future and affirmed the principles they believe are a bedrock of American government and civic life. Bush Hager spoke with Biden, 83; Obama, 64; Clinton, 79; and her father, 79, at a