Demographic appeal. Some of Obama's supporters say the Democratic candidate may move beyond the goal of balancing the ticket. A senior adviser says Obama seems more inclined to pick a sidekick who "fits thematically with what he is trying to project"—change, conciliation, and new ideas. This could mean picking someone such as Sen. Evan Bayh of Indiana, who would appeal to centrists, or Kansas Gov. Kathleen Sebelius or Missouri Sen. Claire McCaskill, who would appeal to women. Former Virginia Gov. Mark Warner, a centrist who is running for the Senate, would also qualify.
Also ran. Obama could go with a candidate who ran against him in the primaries. At the top of the list is Sen. Hillary Clinton of New York, who gathered 18 million votes but fell short. Democratic sources say that at this point, Obama and his aides are not inclined to choose her because of questions about how loyal she and her husband, former President Bill Clinton, would be to Obama. "Actually, their objections have more to do with Bill than with Hillary," says a prominent Democratic strategist. "He showed himself to be demonstrably undisciplined" in the primary campaign.
Other options include Gov. Bill Richardson of New Mexico, a Hispanic who has a sterling résumé as a former member of the House, United Nations ambassador, and secretary of energy. His drawback is that he didn't do well in the primaries this year. John Edwards, the former senator from North Carolina, could add working-class appeal, but he was the vice presidential nominee in 2004 and wasn't considered a huge boon to nominee John Kerry.
Wild card. There are a number of selections that could be dramatic, if risky, game-changers. One is Republican Sen. Chuck Hagel of Nebraska, who appeals to Democratic doves because of his opposition to the Iraq war and whose nomination would extend an olive branch to the GOP. But as Obama operatives road-tested the idea privately on Capitol Hill in late June, they encountered serious resistance from Democrats who said Hagel is too conservative on other issues, especially abortion.
Another name often mentioned is New York mayor and billionaire Michael Bloomberg, who was once a Democrat but switched to Republican and is now an independent. He is widely regarded as a strong, effective manager and had a highly successful business career. But some Democrats wonder if he is temperamentally suited to be anyone's No. 2, and his Jewish faith may be a problem with some voters.
Obama supporters also suggest that former Secretary of State Colin Powell would be a powerful choice. But others argue that Powell tarnished his reputation by arguing that weapons of mass destruction would be found in Iraq, which never happened, and that he is too closely tied to President George Bush.
Republican strategists argue that Obama's choice of a running mate will get him into trouble no matter which way he goes. If he chooses someone young, they say, it will call attention to his own vulnerabilities. If he chooses someone older and more experienced, they argue, it will undercut his theme of breaking away from the Washington elites.
But that's the nature of the vice presidential selection process—it's rarely easy. It provides an insight into a potential president's judgment and ability to handle pressure, which voters consider two of the prime qualifications for the top job.