TAMPA - Mitt Romney's chief strategist Stuart Stevens today downplayed the prospect of a big bump in the polls for the Republican candidate following the GOP convention, contradicting a senior adviser who had earlier cited previous conventions and predicted a boost as big as 11 points.

"I just think all bets are off about any kind of past performance being a predictor of the future," said Stevens, aboard the Romney charter heading to Tampa earlier today. "I think it's extraordinary going into the convention tied or with the lead."

Stevens shifted into a more optimistic tone, saying, "I think if the election were held tomorrow we'd win and win pretty easily. That's amazing considering we've been outspent the way we have been spent, particularly because what the Obama campaign wanted to do hasn't worked."

A CBS News poll released today showed Romney and Obama in a statistical tie, Obama at 46 percent and Romney at 45 percent.

But two weeks ago, on the eve of Rep. Paul Ryan being picked as Romney's running mate, a senior adviser who would only speak to reporters on background, pointed to data that showed challengers usually enjoy the biggest bump from a convention. The adviser told reporters that the Republican convention should be more of a benefit to Romney than the Democratic convention will be for the president.

The adviser estimated a 7 point bump for an incumbent and an 11 point bump for the challenger.

Stevens today also noted the logistics of holding a conventions so close together - as well as the impending hurricane heading for the Gulf Coast - as to why the post-convention bump may not be as big as some might expect.