charade and hillary clinton is testifying to honor the four americans who were killed in benghazi. >> brianna keeler live from washington. another potential challenge to hillary clinton's campaign -- joe biden. the vice president is showing new signs he's ramping up to campaign against her. and some biden allies are already lining up to help. cnn jimmy acosta has more on that. >> reporter: vice president joe biden appears to be beefing up his potential ground operation by lining up the support of the international firefighters union. the group's president says he has spoken to biden in the last few days and the vice president is in his words thoughtfully weighing a bid for the white house. the group's president told us in an interview that they are mobilizing to support biden. here is what he told us a few moments ago. >> we wouldn't be preparing to get into this campaign and to be prepared to support his candidacy unless we were