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Democrat John Kerry's (search) latest television commercial accused President Bush (search) of wanting to send American jobs overseas.

In the same week, a Media Fund (search) ad covered a different topic, criticizing Bush's $87 billion reconstruction plan for Iraq and Afghanistan. A spot by a MoveOn.org (search) affiliate, meanwhile, claimed Bush used the terrorist attacks of Sept. 11, 2001, as an excuse to invade Iraq.

Commercials by such liberal interest groups are meant to hurt Bush and, in effect, help Kerry's presidential bid. But some media strategists acknowledge that such efforts could backfire by muddying Kerry's message of the moment.

Interest groups can't legally coordinate advertising with political campaigns. That means their ads could potentially address different issues than Kerry's commercials, be nastier than his advisers prefer, clutter the airwaves, stray from obvious themes — the economy and national security — or politicize issues Kerry would rather leave alone.

"If I were Kerry's folks, I'd be up nights worrying about this," said Bill Carrick, a veteran Democratic media consultant.

Bush's re-election campaign is now the main Republican voice on the air, but it could face the same difficulty when conservative interest groups start advertising: the inability to ensure that those commercials don't undermine the campaign's strategy.

Since Bush began advertising in early March, Democratic-leaning interest groups and Kerry's campaign combined have together aired enough anti-Bush ads to match the president's commercials in some media markets in battleground states. However, most weeks the groups' ads have been different — in tone, style, topic and images — than Kerry's commercials.

Ideally, media experts say, interest-group ads should carry the same message at the same time the commercial of their preferred candidate is running to boost the odds of influencing voters.

"They would be wise to look at a campaign's themes and try to be consistent about imitating and echoing them without direct coordination," said William Benoit, a University of Missouri-Columbia professor who studies political ads.

David Perlmutter, who teaches communications at Louisiana State University, said not doing so could lead to unintended consequences, such as diffusing a candidate's message or, worse yet, inciting the opposition to turn out to vote. "Sometimes you can be hurt by your friends," he said.

At the same time, Perlmutter added, ads that effectively echo a candidate's focus in a given week could reinforce it.

Last week, an AFL-CIO ad used statements by jobless workers, such as "my industry is pretty much gone," to counter Bush's claim that the economy is "growing stronger." The ad was in 11 of the 17 states where Kerry was running his jobs commercial.

Some interest groups running ads say they're not concerned that they are in conflict with Kerry.

"Obviously since we can't talk (to Kerry's campaign), we can't be absolutely sure of being on the same page. But we're confident over here that we're on the right track in terms of message," said Jim Jordan, a Media Fund spokesman.

MoveOn founder Wes Boyd said his group's primary objective is not to sound the Kerry campaign's lines but to press its members' concerns about Bush's administration — even if doing so doesn't help Kerry. "We let the chips fall where they may," Boyd said.

So far, Democratic strategists say there is no evidence that interest groups have diluted Kerry's message. And, the Massachusetts senator's advisers say they aren't concerned about it. "From what I see, they're raising very relevant issues," said Stephanie Cutter, a Kerry spokeswoman.

Some media strategists say that no matter what issues interest-group ads address, they have one thing in common that could benefit Kerry: They criticize Bush.

"Anything that takes on the president should have the effect of helping the president's opponent," said Steve McMahon, a Democratic consultant.

He and other Democrats said the fact that the interest-group ads cover issues different than Kerry does is proof there is no illegal coordination, as Republicans allege.

Donna Brazile, who ran Democrat Al Gore's campaign in 2000, said interest-group ads may affect what's going on now but won't decide whether Democrats take control of the White House in seven months.

"I do believe it all depends on John Kerry," Brazile said.