With the window of opportunity narrowing for when the presidential candidates must announce their running mates, pundits and political storm chasers are spinning in an attempt to keep up with every clue that might reveal the identities.

The Nashville Post's Web site reported Wednesday that senior campaign officials for Barack Obama are converging in Indianapolis for a "major event" on Saturday, stirring speculation that Indiana Sen. Evan Bayh is the one.

Obama's campaign already announced that he and his running mate-to-be will stop in Springfield, Ill., on Saturday -- and Indianapolis is not so far away.

But the campaign would not confirm or deny the report. And on the Democratic side, Bayh is hardly the only one for whom the stars seem to be aligning.

Delware Sen. Joe Biden, Virginia Gov. Tim Kaine and Kansas Gov. Kathleen Sebelius, along with former Democratic rival Hillary Clinton and others, are high on the list of possible picks.

Reporter's Notebook: House Members Often Overlooked

There were reports late in the day that people were even getting hoax text messages claiming to be from the Obama campaign that announced his selection.

Biden, for one, has practically been on round-the-clock surveillance by the media, desperate for a sign. His stock went up even more after he got a shout-out from Obama, who praised him Tuesday for proposing an additional $1 billion of reconstruction projects in Georgia following the Russian invasion.

The blunt chairman of the Senate Foreign Relations Committee seemed to bat back the speculation Tuesday when he told reporters he's "not the guy." But then he got cagey.

Reporters followed his every move Wednesday. Biden, ever playful, delivered coffee and bagels to the media in the morning, before leaving in his truck to drop off dead wood at a local repository.

"A successful dump!" Biden proclaimed when asked if he had anything to report upon his return. "Dropped everything at the dump, it all worked out."

As reporters shouted more questions, Biden conceded: "That is all I have to report, guys. ... I have not another single thing I can tell you."

But there seemed to be another clue when word broke that Obama would campaign Thursday with Kaine. And then another Tuesday night when Obama used the pronoun "he" to refer to his future running mate.

That would seem to disqualify Clinton and Sebelius.

Even former Clinton spokesman Howard Wolfson told FOX News he doesn't think Clinton will be picked.

"I think it's probably down between Evan Bayh and Senator Biden," said Wolfson, a FOX News contributor.

An Obama aide said reporters shouldn't read too much into Obama's use of that pronoun.

Independent candidate Ralph Nader, for one, told FOX News Wednesday he thinks Obama will pick Clinton.

The Republican guessing game is no less frantic.

FOX News has learned that John McCain will likely announce his vice presidential pick on Aug. 29, his 72nd birthday, in Dayton, Ohio.

His top contenders are said to include Minnesota Gov. Tim Pawlenty and former Massachusetts Gov. Mitt Romney. Less traditional choices include former Pennsylvania Gov. Tom Ridge, an abortion-rights supporter, and Connecticut Sen. Joe Lieberman, the Democratic vice presidential pick in 2000 who now is an independent.

Republican National Committee sources told FOX News that McCain is no longer considering Ridge, saying McCain "got the message" last week that choosing a mate who supports abortion rights would not be received favorably.

But then Lieberman, an abortion-rights support, was added to the speakers list at the Republican National Convention next month in St. Paul, Minn., keeping his name in the mix.

Former New York City Mayor Rudy Giuliani, who has been tapped to give the keynote address at the convention, even told reporters Wednesday that he believes the party could handle an abortion-rights vice presidential candidate.

"And I know John McCain, his seriousness, his love of country - he'll select the person who is best. And if that person happens to be, among other things, pro-choice, the party will support that," Giuliani said on a conference call.

"If John McCain goes with his gut and picks Joe Lieberman, it'll be a gamechanger, and in a positive way," political analyst John Avlon said. "It'll send a message that he is the real centrist in this race."

McCain told radio host Laura Ingraham that he hasn't made a decision.

"And if I say anything more than that I guarantee you there's going to be another one of these firestorms," he added.

Meanwhile, the Obama campaign is clearly enjoying the head fakes.

The presumptive Democratic presidential nominee's campaign toyed with the media on Wednesday, sending out e-mails with suggestive subject lines like "Vice Presidential ..." followed by "Just Kidding" in the body of the message. The Obama camp has told supporters they can sign up for a breaking news e-mail when the vice presidential candidate is chosen.

Click here to read more on the Obama veepstakes.

Click here to read more on the McCain veepstakes.

Click here to read more on House members angling for the VP slot.

Various online trading markets have also been abuzz for months, attempting to weigh the chances of those considered to be in the running for a vice presidential nod.

Here’s a sampling of where the markets stood Wednesday on the Democratic side:

From Rasmussen Markets (value reflects percentage chance)

Delaware Sen. Joe Biden: 37.6 percent

Indiana Sen. Evan Bayh: 19.5 percent

Gen. Wesley Clark: 15 percent

New York Sen. Hillary Clinton: 5 percent

Former Virginia Gov. Mark Warner: 3.8 percent

New Mexico Gov. Bill Richardson: 3.7 percent

Former Vice President Al Gore: 3.6 percent

Former South Dakota Sen. Tom Daschle: 2.4 percent

Former Georgia Sen. Sam Nunn: 1.7 percent

Connecticut Sen. Chris Dodd: 1.3 percent

Virginia Sen. Jim Webb: 1 percent

From Intrade Prediction Markets

Biden: 37.4 percent

Bayh: 19.8 percent

Clark: 13 percent

Clinton: 5 percent

Gore: 3.9 percent

Richardson: 3.9 percent

Warner: 3.8 percent

Daschle: 2.4 percent

Nunn: 2.1 percent

Dodd: 1.3 percent

Webb: 1 percent

FOX News' Aaron Bruns and Bonney Kapp contributed to this report.