After bombarding television viewers with almost $50 million in advertisements for a month, President Bush's re-election campaign is curtailing its ads in 18 competitive states.

Officials say the move, slated to start Friday, follows the campaign's long-term ad strategy to flood airwaves only when voters are paying attention to the presidential race.

"We had planned on doing waves of advertising in higher and lower amounts from the very beginning," depending on "windows of opportunity" when public interest was high, Matthew Dowd (search), the campaign's chief strategist, said Wednesday.

The campaign wouldn't release details, but ad industry sources familiar with the buy say Bush will spend about $4 million to run moderate levels of ads over 10 days compared to the $6 million to $9 million he had been spending each week to saturate broadcast channels in local media markets.

That means viewers could see anywhere from 30 percent to 50 percent fewer Bush ads than they have since the spots started running in early March. His advertising on national cable networks won't change.

Dowd said voters aren't as focused on the race now as they were in early March, when rival John Kerry (searchsecured the Democratic nomination. He said the campaign could increase ad spending should the dynamics call for it.

With the buy, Bush will have spent at least $50 million on TV ads since March 4, far outpacing Kerry, who has spent about $10 million. However, Democratic-leaning interest groups have aired millions of dollars worth of anti-Bush ads.

But as the Bush campaign pulls back, Kerry's campaign plans to increase advertising as early as next week to help flesh out his biography and spell out his message for people who still know little about the senator.

Kerry has been running roughly $2 million worth of ads each week. He's able to boost spending soon because his campaign had collected a Democratic record of some $50 million in the first three months of the year.

Democrats questioned whether Bush's campaign is scaling back advertising for another reason: The ads haven't helped the incumbent Republican gain an edge over Kerry.

Independent polls show the race virtually tied despite the GOP ad blitz. However, Republicans have been able to drive up Kerry's unfavorable ratings during the last six weeks, which pollsters attribute to both Bush's ads and public comments by GOP officials claiming that he supports tax increases and has a habit of changing positions on issues.

Kerry's unfavorable rating went from the low 20s in January to the mid- to high 30s in late March and early April.

The Bush campaign was able to narrow Kerry's advantage on some domestic issues like jobs and health care in some polls in March, but he regained his advantage in more recent polls.

Jim Jordan, the spokesman for several Democratic groups and Kerry's former campaign manager, claimed in an e-mail to reporters that Bush's "multimillion-dollar gamble" to settle the race early with an advertising onslaught had failed.

Dowd said internal polls show the ads accomplished their goal of casting Kerry in a negative light early in the race.

"The two things voters know about Kerry today more than anything else is that he's a flip-flopper and he's going to raise your taxes," Dowd said.