Almost daily, either the Bush campaign or Republican groups roll out ads criticizing Sen. John Kerry (search), and the Democrat's campaign pushes out an ad countering the charges.

While you're likely to catch snippets of the tit-for-tat ads on the news, you'd be hard-pressed to find some of Kerry's responses on the air anywhere else. At least three such ads -- released by the Kerry campaign with great fanfare in the past week -- haven't reached any TV stations.

"The Kerry campaign is trying to have two conversations: one with the press and one with voters," said Evan Tracey, the head of TNS Media Intelligence/Campaign Media Analysis Group (search), which tracks political ads.

Releasing ads that never run or that air only a few times is a common tactic used by campaigns to ensure that their messages -- and not just their opponents' -- get in the news of the day.

Quick and easy to make, ads cost anywhere from $10,000 to $15,000 to produce, but they can receive hundreds of thousands of dollars' worth of free exposure when television news reports on them.

President Bush's (searchcampaign also has used the tactic, but to a much lesser extent. In July, the campaign got loads of free exposure from an ad suggesting that Sen. John McCain was Kerry's first choice for the ticket, not Sen. John Edwards. The ad-tracking company said it ran only 15 times on cable stations.

This month, Kerry's campaign has responded to nearly all critical ads ever since former aides to President Clinton -- known for a "rapid response" strategy in the 1990s that left no charge unanswered -- joined the Democrat's team.

Kerry's campaign got burned in August when it waited two weeks to answer ads by Swift Boat Veterans for Truth (search) that questioned his Vietnam service. The criticism took hold and Bush took the lead in polls.

Now, Kerry's campaign is whipping out TV ads nearly every day, many countering other spots. The campaign has released at least 15 TV ads in the past 14 days.

A week ago, Bush rolled out an ad that used pictures of Kerry windsurfing to illustrate Bush's claim that the Democrat's positions shift "whichever way the wind blows." Hours later, Kerry's campaign pushed out a commercial condemning Bush for "a juvenile and tasteless attack ad."

Bush's ad is running in more than a dozen states. The Kerry campaign said its ad would run wherever Bush's did, but the response has yet to air.

Over the weekend, a group of Republican insiders, Progress For America Voter Fund (search), aired in Iowa and Wisconsin an ad that showed Al Qaeda leader Usama bin Laden and other terrorists. It asked, "Would you trust Kerry against these fanatic killers?"

Kerry's campaign furiously put together an ad -- on a weekend -- that accused Bush and Vice President Dick Cheney of "despicable politics" and "playing politics with the war on terror." But that spot never ran either.

Neither did one on Monday that was meant to answer a Bush ad that pieced together several comments Kerry had made about Iraq.

"We decided that Bush's ads don't work and our better response was the one we already had on the air," said Debra DeShong, a Kerry spokeswoman.

Other Kerry campaign spots haven't run long enough to make an impression on voters.

The campaign's ad criticizing Cheney's links to his former company, Halliburton (search), ran only twice -- once in Oregon and once in Pennsylvania. The campaign said it pulled the ad because NBC objected to its use of network footage, but aides say the ad was slated to run only briefly.

Meanwhile, Kerry's campaign has put on the airwaves two new ads that contain sharp accusations against Bush over the war and his ties with Saudi Arabia.

One claims the president's "attack machine is smearing" Kerry and that Bush "misled us about weapons of mass destruction," while saying that Kerry "offers a fresh start" in Iraq. In another spot, Kerry says, "I want an America that relies on its own ingenuity, not the Saudi royal family."