A Sibelius or Napolitano choice is by no means inevitable: There are lots of other choices out there, and plenty of pundits eagerly predicting them. But the most enthusiastically pushed candidates tend to come with huge negatives attached to them, as Obama, D-Ill., well knows.

First, forget the supposed "dream team" choice of Sen. Hillary Clinton, D-N.Y. That looked quite possible as Obama headed for victory in the final primaries. But if there was a single deal-breaker moment to that choice, it was when Clinton publicly cited the fate of Sen. Robert F. Kennedy in 1968 as a reason she should stay in the race. Kennedy, D-N.Y., was assassinated right after winning the California primary.

Clinton's comments understandably outraged the Obama camp. They also outraged the Kennedy family, many of whom have been prominent in supporting Obama. And it looked like a public rebuke, or even repudiation, of Clinton when Obama announced that of all people he was choosing RFK's niece, Caroline Kennedy, the daughter of President John F. Kennedy, to help him pick his vice presidential running mate.

Also, since then, national opinion polls have shown Obama climbing ahead of his Republican opponent, Sen. John McCain of Arizona. It is not a decisive lead at this early point in the race by any means, but it does mean that the old argument -- which we have previously noted -- that Obama needed Clinton to win the support of women voters who had backed her didn't seem to apply anymore.

More important, the Obama inner circle now clearly believes they don't need Clinton to unify the party and win her supporters. That means she's out.

If Clinton is out, then two other often-suggested running mates may be out, too. They are former NATO commander Gen. Wesley Clark from Arkansas and New Mexico Gov. Bill Richardson. Both are impressive figures with great experience. Indeed, we think either of them would make an excellent running mate and vice president. But Richardson has shown repeatedly he has no coattails worth the name among Hispanic voters or across the Southwest. And he and Clark would both come with strong historic ties to the Clintons.

Clark can still not be ruled out: He's from the Southeast heartland and has a very impressive military record. But his own campaign in 2004 went nowhere. Both men are also seen as figures of the old Washington establishment and the Clinton era, and Obama's campaign is focused so much on the themes of change and renewal in Washington, both could be an embarrassment to him.

Forget Sen. Jim Webb, D-Va.: He is tremendously impressive and a figure of great moral stature in the Senate after only two years in the chamber. But he is a maverick who has outraged many core Democrat constituencies. He won his own Senate election by the narrowest of margins in 2006 -- a victory we predicted at the time in the face of all Conventional Wisdom -- and we expect him to be re-elected by a landslide in 2012.

However, like Clinton, Webb would be too much his own person as vice president and could be an unpredictable bull in a china shop during the campaign. Obama has shown he is determined to be master in his own house, and no one has ever been Webb's master.

Also forget Sen. Chuck Hagel, R-Neb. Hagel is an admirable man, a Vietnam combat vet and an outspoken critic of the Iraq War. He and Obama are warm friends. He might even be offered a senior Cabinet position in the Obama administration.

However, Hagel is a terrible campaigner, takes forever to make up his mind, and puts even sympathetic audiences to sleep. In terms of charisma, he makes Sen. Joe Lieberman, I-Conn., who was Vice President Al Gore's running mate in 2000, look like Brad Pitt.

Hagel has no coattails in the conservative community to offer Obama, and picking him risks alienating hard-core Democratic constituencies who supported Clinton in the long five-month primary and caucus struggles and who Obama must win back.

That leaves Sebelius and Napolitano as attractive choices. Napolitano, coming from McCain's home state, offers the prospect of hurting him hard throughout his own traditional base of the Southwest. She is prominent in urging strong border security, an issue where McCain is vulnerable even among hard-core Republicans, and she will energize the women's vote. Italian-Americans may flock to her, too.

Sebelius has been a big hit in Kansas and is respected throughout the Midwest, one of the pivotal areas of the country that Obama must win. She is seen as a strong campaigner. Like Napolitano, she would impress women voters and core heartland Democrats. Her regional coattails in the Midwest far exceed those of Richardson in the Southwest or Clark in the Southeast. And it wouldn't hurt that both Sebelius and Napolitano are experienced successful governors.

Finally, neither of the lady governors will overshadow Obama on the ticket. For another negative Clark and Richardson would both carry is that the very experience they bring would draw attention to Obama's own lack of it. And either Sebelius or Napolitano would be a fresh face in national politics offering new hope and energy.

Obama, of course, still has every freedom and opportunity to pick one of the other front-running possibilities, or someone else entirely. After all, no one saw Sen. Dan Quayle, R-Ind., coming in 1988 or former Defense Secretary Dick Cheney in 2000. But when looking at Sebelius and Napolitano, as legendary UPI veteran Damon Runyon famously said, "That's the way to bet."