 None have called on him to bow out of the race. But pressure is growing for the White House to address concerns that a poor Biden performance could damage down-ballot candidates as well. Among them, Democrat Senators Jon Tester of Montana and Sherrod Brown of Ohio. Flipping their vulnerable seats would likely allow Republicans to reclaim the Senate majority. Bob Agnew reporting. Late Wednesday, Vermont Senator Peter Welsh called on Biden to withdraw, becoming the first Senate Democrat to do so.