WASHINGTON (AP) -- Presidential candidate Barack Obama says his pick for a running mate - he's made a decision but isn't giving out a name just yet - had to meet three standards to join the Democratic ticket: Prepared to be president, able to help him govern and willing to challenge his thinking.
Those criteria did little to narrow the guessing game as Obama prepared for a massive rally in Illinois on Saturday to present his No. 2 to the nation and undertake a pre-convention tour of battleground states. He planned to disclose his choice by unleashing text messages to supporters, perhaps as early as Friday.
"Obviously, the most important question is: Is this person ready to be president?" Obama said in an interview aired Friday on "The Early Show" on CBS.
"The second most important question, at least from my perspective, is: Can this person help me govern?" he said. "Are they going to be an effective partner in creating ... economic opportunity here at home and guiding us through some dangerous waters internationally?"
Obama said he also wanted someone who would show independence. "I want somebody who is going to be able to challenge my thinking and not simply be a 'yes person' when it comes to policymaking," he said.
On Thursday, Obama was nonchalant as he campaigned with one contender considered to be on his short list, Virginia Gov. Tim Kaine.
"I've made the selection, that's all you're gonna get," Obama told The Associated Press.
The Illinois senator wouldn't say whether he'd offered the job to his pick or when exactly he would tell the world.
"Wouldn't you like to know?" he told the AP, with a grin.
On the Republican side, GOP officials said late Thursday that John McCain had not settled on a running mate although former Massachusetts Gov. Mitt Romney and Minnesota Gov. Tim Pawlenty were under serious consideration. Two officials close to Romney said he had not been offered the job.
It's likely McCain will wait to see who Obama selects before picking his running mate.
The Arizona Republican is expected to announce his choice between the Democratic National Convention that begins Monday and his own GOP coming out party in St. Paul, Minn., that begins Sept. 1. It's possible he could do it on Friday, Aug. 29, the day he turns 72 and also the day after Obama accepts his own nomination in Denver, but no plans are set and he could wait until his own convention week.
Republican and Democratic officials said both candidates were capable of making wild card picks that would surprise their backers. And, although it appeared unlikely, Obama's vanquished rival Hillary Rodham Clinton still could emerge as his No. 2.
One person who had been vetted for the position told The Associated Press there had been no contact from Obama or his campaign about the decision. The person spoke on condition of anonymity because the Obama campaign asked candidates not to talk about the decision.
The Illinois senator was widely thought to be considering Kaine, Gov. Kathleen Sebelius of Kansas and Sens. Joe Biden of Delaware and Evan Bayh of Indiana. None of them gave anything away - at least not in words.
Obama spent part of the day with Kaine, who reportedly told a colleague Wednesday that he believed he was on the short list. West Virginia Gov. Joe Manchin said Kaine told him although he hadn't heard anything from the Obama campaign on where he stands at the time, "he really thinks he has a chance at the short straw."
Kaine and Obama met privately with the governor's staff for 15 minutes at a Richmond hotel. Afterward, Kaine said he would let the Obama campaign speak about whether the candidate asked him to be his No. 2. But two people close to Kaine said the governor was still in the dark.
Kaine plans to fly Friday night directly from Virginia to Denver, site of next week's convention, three people with knowledge of the governor's travel plans said. The plans could be changed if Kaine is told he needs to fly to Springfield, Ill., for the Saturday rally instead.
Biden had a family gathering at his home Thursday afternoon, with his wife Jill, niece Missy Owens and son Beau, Delaware's attorney general, coming and going past reporters staked outside.
Sebelius, campaigning for Obama in Iowa, said being mentioned as a potential running mate is something of "an out-of-body experience." She said she would leave the announcement to the campaign.
Bayh worked in his Capitol Hill office and later spent time at his home in Washington. He left wearing shorts and a baseball cap but told reporters outside he had no news to share. "Not tonight, sorry," he said.
Two dark horse candidates appeared out of the running.
Former Georgia Sen. Sam Nunn's spokesman said he would be traveling internationally until Monday, making a Saturday visit to Springfield seem unlikely. And, Sen. Jack Reed of Rhode Island, a national security expert, was at his home in Jamestown on Thursday. He told an AP reporter that he was not Obama's choice and that he had not been asked for any background information.
Associated Press writers Bob Lewis in Virginia; Nedra Pickler in Chicago; Beth Fouhy in Emporia, Va.; Larry Messina in Charleston, W.Va.; Randall Chase in Greenville, Del.; Mike Glover in Des Moines, Iowa; Ray Henry in Jamestown, R.I.; and John Hanna in Topeka, Kan., contributed to this report.
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