Ever since Sen. John McCain named Gov. Sarah Palin as his vice presidential running mate, quickly shifting excitement and momentum to the GOP ticket, there's been a rumor that just won't go away. The rumor has been growing on the Internet, and has been circulated countless times via e-mail.

Throughout the month of September, an email entitled "Rumor Has It?" has been making the rounds of inboxes, which claims that Sen. Barack Obama's VP running mate, Sen. Joe Biden, will step out of the race shortly after the VP debate on Thursday, "probably around Oct. 5".

According to the unverified e-mail, Biden will cite health concerns. Biden did suffer from two brain aneurysms and was hospitalized 20 years ago, but hasn't had any major issues in recent years. Vacating his VP spot at the last minute would leave it open for Obama to make a last minute move of his own - putting a woman on the ticket.

Now should this all go down, the replacement choice could be either NY Sen. Hillary Clinton or Kansas Gov. Kathleen Sebelius. Most are saying it would be Clinton.

The entire idea that Biden would ditch his running mate at the last minute, and that Obama would have a change of heart and pick Clinton to run with him sounds beyond ridiculous. But it would be an ingenious move, possibly bringing back many of Clinton's 18 million disillusioned supporters, and ensuring wins in key battleground states.

The last time such a running mate switch occurred was in 1972, when Democratic presidential candidate Sen. George McGovern replaced Sen. Tom Eagleton with Sargent Shriver. This new ticket didn't stand a chance against Republican Richard Nixon, and was annihilated on election day. So while a switch does hold exciting possibilities, it wouldn't come without danger.

Nevertheless, as much as many would like this rumor to become true, the Obama campaign dismisses the e-mail as "not true" and an "Internet rumor." The only thing that possibly gives this rumor any credibility is Biden's series of slips and screw-ups since being named Obama's VP running mate, including:

• Saying Obama should have picked Clinton instead.
• Praising Sen. McCain, repeatedly.
• Taking a position to Obama that matches the GOP on at least one issue.
• Publicly saying he disagreed with an Obama TV ad.

I won't say that this could NEVER happen, it seems illogical to me, but we all know that the Obama campaign isn't much good at keeping a secret, what with the failed text message announcement at all. So who knows what could happen!