Voters in this critical swing state are bombarded daily with TV messages and visits by presidential candidates and their surrogates.

John McCain and Barack Obama are so eager to win over Ohioans that the senators spent at a combined rate of almost $24,000 every hour last week to air television advertising in the Buckeye State.

To reinforce the messages, they're on the ground here, too.

Republicans McCain and Alaska Gov. Sarah Palin were in a Cleveland suburb yesterday. She will be in Wilmington today and in southeastern Ohio on Sunday. Obama will tour the state today and Friday, making stops in Dayton, Cincinnati, Portsmouth, Chillicothe and Columbus. And the Democrat is coming back next week.

The $4 million in total ad spending -- $2.2 million by Obama and $1.7 million by McCain -- was the most in any state during the week of Sept. 28-Oct. 4. Next in line was Pennsylvania, where the campaigns spent a combined $3.8 million, according to statistics compiled by the Wisconsin Advertising Project at the University of Wisconsin-Madison.

At the same time, the analysis showed that nearly all of the ads McCain aired nationwide were negative or attack ads. About one out of three of Obama's ads were negative. The balance is much more even over the course of the campaign, with 73 percent of McCain's ads viewed as negative, compared with 61 percent for Obama.

The project analyzes TV advertising data from 186 media markets across the country.

Ken Goldstein, director of the project, said advertising by both candidates is ramping up as the election approaches.

Obama, of Illinois, spent $17.5 million nationwide last week, while McCain, of Arizona, and the Republican National Committee combined to spend $11 million on his campaign. The Democratic National Committee has spent very little on Obama's behalf, the project found.

The combined $28.3 million was nearly double the $15.5 million spent by the candidates the first week in September. And it was $10 million more than President Bush and John Kerry spent during a similar seven-day period in the 2004 presidential race.

"Ten of the 15 states where both candidates are advertising were won by Bush," Goldstein said in a statement. "The campaign is being played on the Republican side of the field this year."

Indiana, Iowa, Michigan, Minnesota, Ohio, Pennsylvania and Wisconsin were hit heavily with ads, with McCain spending more than 60 percent of his money there; Obama spent about 47 percent.

In the Columbus metro market, 1,106 presidential campaign commercials aired last week, making it 14th in the nation. Las Vegas had 2,020, the most of any single market.

Goldstein said third-party groups are not playing nearly as significant a role as they did in the 2000 and 2004 elections. Vets for Freedom, which supports McCain, spent $1 million on ads. A group called Defenders of Wildlife aired $34,000 worth of pro-Obama ads, most of them in Ohio, the project found.

ajohnson@dispatch.com