HY VEE HALL, DES MOINES -- 1300. It's the number that best explains the maximal effect that Oprah Winfrey's appearance here with Barack Obama will have on the Iowa caucuses.

Between the day three weeks ago when the Winfrey-a-thon was announced and today, the Obama campaign signed up more than 1300 new volunteers directly through the media of pre-Oprah publicity.

And the second number to keep in mind is the roughly 12,000 new names and e-mail addresses that the Obama campaign obtained in the Des Moines area alone in exchange for tickets. Many were Republicans and were curious. (At least one was Australian and thus ineligible to vote.)

The massive amount of media attention was almost tertiary, although every network evening newscast has done at least two stories about the campaign stops during the past two days.

As Oprah Winfrey introduced Obama, his chief strategist David Axelrod stood on the press riser, beaming. Paul Tewes, Obama's Iowa state director, stood

“Despite the speculation and the hype, I understand the difference between a book club and free refrigerators,” Oprah began, “I understand the difference between that and this critical moment in our nation’s history.”

A few minutes later: "I'm here to tell you Iowa, he's the one."

18,500 people went wild.

I asked one of Obama's senior advisers whether he was surprised that the Clinton campaign had tried to bracket the doubles Os by bringing Chelsea Clinton to Iowa this weekend.

"Nah. It's kind of like bringing a knife to a bazooka fight."