Last month, McCain told reporters he was in the "embryonic stages" of the search with a list of about 20 names.

At one point, McCain let slip that as he learns about the process of picking a running mate, he'd like to speak to A.B. Culvahouse, who has been involved in vice presidential searches before and served as counsel to President Reagan from 1987-1989. Several Republicans close to the campaign say that while McCain and Campaign Manager Rick Davis are running the show, Culvahouse is involved in the process.

Obama is still engaged in an all-but-decided nomination campaign against Clinton, with three primaries left in Puerto Rico, South Dakota and Montana. The voting ends June 3.

Clinton spokesman Howard Wolfson said Obama's vice presidential selection process "is clearly premature in that he is not yet the nominee." He also said the Clinton campaign didn't have a similar process under way and there had been no discussions with the Obama people about her becoming the Illinois senator's No. 2.

Some in the party are calling for Obama to pick Clinton, but others say that couldn't work after their long and heated campaign against each other.

Other possible options are governors such as Janet Napolitano of Arizona, Kathleen Sebelius of Kansas and Tim Kaine of Virginia; foreign policy experts including former Georgia Sen. Sam Nunn, Connecticut Sen. Chris Dodd or Delaware Sen. Joe Biden, or other senators such as Missouri's Claire McCaskill or Virginia's Jim Webb.

Obama could look outside the party to people such as Hagel or independent New York Mayor Mike Bloomberg. Or he could look to one of his prominent supporters such as former Sen. Tom Daschle of South Dakota or 2004 vice presidential nominee Edwards. He also could try to bring on a Clinton supporter such as Indiana's Sen. Evan Bayh or retired Gen. Wesley Clark.

House Speaker Nancy Pelosi indicated to reporters Thursday that she thought the timing was right for a veep search, even as she was careful not to play favorites.

"This election is right around the corner, and a new president will be sworn in in a matter of months," said the California Democrat.

Asked if she'd be interested in the running mate spot, she replied, "Are you kidding? Being Speaker of the House is the best job in the world. Why would I want to be No. 2?"

The veep search is one of many steps the Obama campaign is taking toward the general election, with just 61 delegates needed to clinch the nomination according to the latest Associated Press count. Obama has 1,965 delegates to Clinton's 1,780, with 2,026 required to secure the party's nod under Democratic National Committee rules.

The Obama campaign is rapidly adding to its campaign staff, both at the headquarters and in swing states. Obama plans to mix primary and general election campaign travel in the next week, with stops in Nevada, New Mexico and Colorado.

The campaign also is registering voters across the country for the November vote. And top Obama organizer Paul Tewes is in discussions to run the fall campaign for the Democratic National Committee.