Since the invention of the remote control, political campaigns have had a tough time persuading viewers to sit and watch their television ads rather than switching to another channel.

Now, the growing popularity of fast-forward, ad-skipping digital video recorders, including the technology's pioneer TiVo Inc., is forcing campaigns to rethink where and when they advertise. Viewer habits on using these DVRs are a critical part of any election strategy.

"Twenty years ago, most people had three or four viewing options and had to get up and walk across the room to change the channel," said Steve Murphy of the Alexandria, Va.-based political consulting firm Murphy Putnam Shorr.

One calculation for campaigns is what shows DVR owners typically record and watch at a later time when they're more likely to skip all the commercials. Television analysts say viewers are less likely to record live telecasts such as sports events, newscasts and entertainment programs like "American Idol."

In the remaining months of this election year — and looking ahead to the 2008 presidential campaign — political ads are more likely to show up on these programs, said Murphy, who counts Tennessee Democratic Gov. Phil Bredesen's re-election campaign among the dozen races for which he is consulting this year.

Seven years after being introduced as a niche product, DVRs are now used in one in eight TV households.

Josh Bernoff, principal analyst at Forrester Research Inc., projects DVR usage to increase to one in five households by the end of this year, and to double to nearly 40 percent by 2008. More than half of all TV households are projected to have DVRs by 2010.

Carefully choosing when to advertise on television may stop the bleeding in the short term, Bernoff said, but he expects overall television advertising to decline as DVRs become more popular.

"I think the real question is: Do you really want to be pumping more money in search of a smaller audience?" he said. "Or should you take advantage of the trend and move into other media?"

Bernoff said Internet video provides advertisers with a feature that DVRs can't offer: spots that can't be skipped.

"Video advertising on the Internet — which tends to be 15 or 20 seconds before a clip — is not skippable. People actually sit through it," he said. "That might have a higher degree of yield than what you get from a television ad."

Internet advertisers also have the advantage of being able to count the exact number of times an ad has been seen, Bernoff said.

Comcast Corp., the nation's largest cable operator, is trying to revitalize political ad sales by creating an "Elections 2006" video-on-demand offering. Video-on-demand lets digital subscribers watch archived programs at any time, and Philadelphia-based Comcast is hoping campaigns will want to buy spots up to an hour long.

One of three Democrats running for lieutenant governor in Massachusetts, Cape Cod businesswoman Andrea Silbert, has purchased on-demand advertising, but Comcast officials couldn't tell The Associated Press how much uptake there has been on the "Elections 2006" feature systemwide.

Hollywood-based political consultant Fred Davis said he isn't certain that DVR usage will seriously affect campaign media strategies this campaign cycle, but he recognizes the disruptive trend.

"I think the day will come, and it's not a day I'm looking forward to," said Davis, whose Strategic Perception Inc., is consulting for Jim Bryson, the Republican gubernatorial nominee in Tennessee. "It's already an issue for the Budweisers and the Fords."

But Davis has had successes in producing not-for-broadcast campaign videos. Davis in 2002 created a 10-minute video for Georgia GOP gubernatorial candidate Sonny Perdue that depicted incumbent Democrat Roy Barnes as a rat climbing the Capitol dome.

The "King Rat" video never aired on TV, but it was spread over the Internet and burned onto DVDs. It's considered one of the highlights in Perdue's defeat of Barnes, despite being outspent $20 million to $3.65 million.

Both Murphy and Davis say it's unlikely political campaigns will create the two- to five-second ads some commercial advertisers are considering placing at the very beginning or tail-end of a commercial break to try to catch viewers attention as they scroll through the ads.

The problem, Murphy said, lies in trying to say "something meaningful" about a candidate in five seconds.