Will he pick someone with expertise in foreign policy or national defense to offset his lack of experience? A governor from a battleground state with executive experience? How about a former rival -- maybe named Clinton?

Obama won't talk about it yet, even if he's secretly running through the pros and cons of different names. That would appear presumptuous, even arrogant, as long as New York Sen. Hillary Clinton says she's still in the race.

"We haven't wrapped this thing up yet," he said Thursday in an interview with CNN. "At the point where I'm the nominee I'll start going through the process of figuring out what my running mate, who my running mate might be."

Nonetheless, he's started talking like he's looking beyond the primaries to the general election. Analysts agree and note that the first step to the fall campaign is picking a vice presidential candidate.

Here's a list of possible Obama running mates, with pluses and minuses:

• Sen. Joe Biden, 65, of Delaware

With 36 years in the Senate and much of it spent on the Foreign Relations Committee, Biden has long experience in foreign policy circles. "He'd rather be secretary of state, but he'd accept it," said a Biden adviser who spoke on condition of anonymity.

Downside: During his unsuccessful bid for the nomination he curbed his tendency to talk too much, but the muzzle could fall off.

• Retired Army Gen. Wesley Clark, 63, of Arkansas

As NATO commander, Clark oversaw the allied air war against Serbia that toppled dictator Slobodan Milosevic. He also ran for the nomination in 2004 and won a primary in Oklahoma. As a Clinton backer this year, he could help repair relations with Clinton supporters.

Downside: He had testy relations with other military officers that could come back to haunt him.

• Sen. Hillary Clinton, 60, of New York

She has deep support from working-class whites, women and older Democrats. Having her on the ticket could unify the party.

Downside: Obama and Clinton clearly don't get along, and a scorched-earth campaign against him in the final weeks of the campaign would make that worse. Also, nobody knows how former President Bill Clinton would fit into an Obama administration.

• Sen. Claire McCaskill, 54, of Missouri

An early supporter of Obama from a critical battleground state. She's also a Roman Catholic -- a swing voting bloc.

Downside: Elected in 2006, she has even less experience in national office than does Obama, elected two years earlier.

• Gov. Bill Richardson, 60, of New Mexico

The resume candidate, with legislative experience in Congress, diplomatic experience at the United Nations and abroad, and executive experience as secretary of energy and governor. Also comes from a swing state and speaks to Hispanics, a key group Obama needs.

Downside: He couldn't win a single primary himself.

• Gov. Kathleen Sebelius, 59, of Kansas

Popular two-term Democrat found a way to win in the heart of Republican country. Her father, John Gilligan, was governor of Ohio, a swing state in the fall. Kansas was the home state of Obama's mother.

Downside: She shares with all potential female running mates the possible liability that adding a woman to a ticket headed by an African-American might be overloading it with too much change for America to swallow.

• Gov. Ted Strickland, 66, of Ohio

A popular governor of a critical battleground state, Strickland is a former Methodist minister who can speak to churchgoers often uncomfortable with the traditionally secular Democratic Party.

Downside: It's debatable whether any vice presidential candidate could deliver his home state.

• Sen. Jim Webb, 62, of Virginia

A former secretary of the Navy under Ronald Reagan, Webb also was a Marine whose service in Vietnam was chronicled in the same book that highlighted McCain's service, The Nightingale's Song. He also opposed the Iraq war like Obama and is popular in Virginia, a traditionally Republican state in presidential elections that Obama hopes to win.

Downside: Elected to office for the first time just 18 months ago, Webb is a political newcomer who sometimes has struggled to control his temper.