He is costing Giuliani most: A third of Thompson's supporters say they would otherwise back the former mayor. Giuliani leads the field at 28%, down 4 points from two weeks earlier. Thompson is second at 19%, up 8 points. McCain is at 18%, 1 point lower. Former Massachusetts governor Mitt Romney is fourth at 7%, down 5 points. The Democratic contest generally has been stable, though a USA TODAY Poll taken June 1-3 had shown Obama 1 percentage point ahead of Clinton, 30%-29%. In the new survey, Clinton leads Obama 33%-21% if former vice president Al Gore — who has neither entered the race nor ruled it out — is included among the candidates. She leads by 39%-26% if Gore isn't included. Former North Carolina senator John Edwards is then third at 13%.