OBAMAS PROBLEMS plus video

Despite Obama's successes so far, it's hard to argue with Bill Clinton that it's a "roll of the dice" to vote for a freshman senator less than four years removed from the Illinois legislature. Obama still has much to prove. The potential for setbacks and mistakes is high.

REZKO: Obama's relationship with indicted businessman Antoin "Tony" Rezko threatens his image as an antidote to the poisons of Washington. Rezko, accused of scheming to pressure companies seeking state business for kickbacks and campaign contributions, poured thousands of dollars into the campaigns of Obama and others. Rezko also helped Obama increase the size of his yard in a transaction that the Illinois senator now calls a "boneheaded" mistake.

RECORD: Scrutiny of Obama's record will increase with each step he takes toward the Democratic nomination. The New York Times recently poked holes in Obama's explanation of his role in legislation that ultimately benefited a nuclear energy company whose executives and employees have donated more than $200,000 to his campaigns.

RACE: Obama makes history with every victory as the first black candidate with a serious shot at the White House. But the question persists: Can a black man win it all? Obama drew support from four in 10 whites across 16 states _ more than he had captured in earlier primary states. He and Clinton tied among white men while Clinton led among white women. Clinton won six in 10 Hispanic voters, a crucial group that helped her win in California and Arizona.

TEMPERAMENT: Unlike his rival, Obama has never experienced a tough campaign _ and it shows at times. Remember when he said in New Hampshire that Clinton was "likable enough"? It grated on female voters. He needs to avoid looking rude, crabby or cocky. His friends would tell you that's not always easy for him.

EXPERIENCE: The unusually self-aware Obama acknowledged last summer that it was "a stretch" for voters to consider him for the presidency. He needs to avoid a miscue that underscores his inexperience. About one-fifth of the Democratic voters Tuesday said they favored a candidate with seasoning, and Clinton won nearly all their votes.