Bill Clinton campaigned in Arkansas this week, focusing on college campuses and urging students to support candidates like Mark Pryor, one of the most endangered Democrats in the Senate. At each stop, staffers scurried through the crowds, gathering email addresses and cellphone numbers that could be used to mobilize voters on Election Day.In Wisconsin, where Democrat Mary Burke has a shot at deposing the Republican governor, Scott Walker, Michelle Obama struck a similar theme aimed at young women and blacks. "When we stay home, they win," she told a large crowd at a Milwaukee convention center.This is a hard year to be a Democrat.