 Fox News. I'm Sue Guzman. President Biden's digging in, dismissing concerns from fellow Democrats and others calling for him to bow out of the race. Fox Business Network's Hillary Vaughn reports. President Biden is trying to whip his party into shape, telling donors he's not going anywhere, daring any opposers to challenge him at the convention on national TV and firing off a letter to all congressional Democrats warning that an attack on him as the nominee