Race injected into campaign

Fresh off of a decisive victory in the Mississippi Primary, Barack Obama is now hoping to secure a win in Pennsylvania-- whose Primary will take place in less than six weeks. But standing in the way -- is Hillary Clinton-- who leads Obama by double digits in most recent polls. SOUNDBITE: Hillary Clinton, presidential candidate, saying (English): "I am thrilled to be back in Philadelphia." In Philadelphia - race was once again injected into the campaign, as Hillary Clinton had to explain comments by a prominent supporter and fundraiser, Geraldine Ferraro - who was Walter Mondale's 1984 running mate. In a newspaper interview, Ferraro insisted that Obama had gotten so far in the campaign because of his race. Senator Clinton called the comments "regrettable." SOUNDBITE: Hillary Clinton, presidential candidate, saying (English): "Well, I didn't say it. And I regret that it was said and I obviously reject that, I don't agree with that." But Obama's campaign said the Clinton statement did not go far enough. SOUNDBITE: Susan Rice, Obama advisor, saying (English): "That's a really outrageous and offensive comment. It is the sort of comment, that we have heard, repeatedly, I'm afraid, from some of the Clinton surrogates." In fact, surrogates for each campaign have -- in just the last two weeks alone -- made statements that have led to apologies being issued. The Brooking Institution's Thomas Mann. SOUNDBITE: Brooking Institution's Thomas Mann saying (English): "They certainly caution their staffs and advisors and surrogates ahead of time to avoid certain things. And that's the most they can do. But in other cases, some of the comments may be strategic." But for the next six weeks, the focus for the candidates themselves remains Pennsylvania and the 158 delegates that are at stake there. A win by Obama could essentially push Clinton out of the race -- making him the presumptive nominee.