Obama campaign manager David Plouffe announced the advertising buy this morning, saying the campaign would also relaunch advertising in Georgia, where it hasn't advertised in several months, and also start advertising in North Dakota.
The surprise add is Arizona, but recent polls have indicated the state, while still leaning toward Mr. McCain, is getting closer.
"We think things have been tightening up there," said Mr. Plouffe. He also cited heavy voting by Hispanics and suburban votes that may benefit the Obama campaign. "If someone else were the nominee, [Arizona] would be a core battleground."
He said the ad wouldn't attack Mr. McCain, but would be positive.
"It's enough in the realm of the possible that we want to put a little extra effort at the end," he said. "We want to give it a go in the last few days. We wanted to see how far we can go."