Biden's VP search puts spotlight on how long he'll serve
FILE - In this March 7, 2020, file photo Democratic presidential candidate former Vice President Joe Biden acknowledges the crowd during a campaign rally in Kansas City, Mo. But the question of his long-term prospects looms over his candidacy, especially as he considers his options for vice president. None has passed up a chance at a second term after just four years in the White House since shortly after Reconstruction. If Trump secures a second term, Vice President Mike Pence would seem to be a natural successor. Bush is the only sitting vice president in modern history to be elected president.