President Bush took his message of a rebounding economy to four presidential battleground states Monday with new radio ads that assail Democrat John Kerry (search) for "talking about days of malaise and the Great Depression."

The ads were running in Colorado, where Kerry was campaigning about stem-cell research; Ohio, where Bush was raising money for the Republican Party; and Nevada and Missouri, two states where Vice President Dick Cheney (search) was speaking about homeland security and attending a campaign rally.

Ads for two other states are planned for later this week.

The radio commercials come as Bush's re-election campaign pauses its television advertising for several days starting this week following an $80 million barrage of TV commercials.

So far, Bush has spent more than $2 million to run several weeks of radio commercials, not including the latest ads. Kerry's campaign has not run any general election radio ads, and political analysts say the Democrat may be missing out.

"When people are driving, they tend to listen, and you've got more of a captive audience rather than television, where people graze," said Tom McPhail, who teaches political communication at the University of Missouri.

Radio also allows campaigns to spend more time explaining their viewpoints, compared with the typical 30-second TV ad, and it requires listeners to think about what they're hearing, unlike TV, which often does viewers' work for them through visuals, McPhail said.

Darrell West, a political science professor at Brown University, said radio also gives campaigns tremendous targeting power — both geographically, depending on media markets, and demographically, based on the formats of radio stations like country or all-news.

"In recent elections, radio has become very popular because you can deliver messages below the media radar," West said, noting that some of the most negative and misleading ads have been done through radio.

Bush's new radio ads are a version his latest TV ad about the economy.

"After recession, 9-11 and war, today our economy has been growing for 10 straight months," the radio ads say. "We've met serious challenges and things are beginning to turn around."

The ads then are tailored to each state. For example, one ad says: "Here in Nevada, things are looking up, too. The economy has added 50,000 more jobs than a year ago and the unemployment rate has dropped below the national average to 4.1 percent."

At the end, the ads mock Kerry: "What does John Kerry say? He's still pessimistic, on a misery tour talking about days of malaise and the Great Depression."

Chad Clanton, a Kerry campaign spokesman, rebuked the Bush campaign's assertion that the economy is strong. "It's not strong for most of the middle class. Bush is satisfied with where we are, but Kerry believes we can do better," he said.