Four years ago, the six major candidates for L.A. mayor took to the airwaves with a weeks-long barrage of television advertising that cost more than $7 million by primary day.

This year, a smaller field is on track to spend slightly less money over a shorter period, according to political consultants and station executives.

The change is driven by several factors: a 15 percent to 20 percent increase in ad rates since the last campaign, higher name recognition among this year’s contenders, and a new “people meter” system for measuring television audiences.

“As far as the number of different commercials, it’s actually pretty small,” said Steve Huerta, who coordinates political ads for Viacom Inc.’s KCBS (Channel 2) and KCAL (Channel 9). “Usually, a campaign will see what the other campaigns are doing and respond to something at the last minute,” Huerta said. “That just isn’t happening in this race.”

In 2001, the six candidates struggled to define themselves to the famously fragmented Los Angeles electorate in an election with no incumbent.

This year, Mayor James Hahn and City Councilman Antonio Villaraigosa are airing two television spots each. State Sen. Richard Alarc & #243;n, who has raised far less than other major challengers, has two 15-second ads in limited rotation.

Former state Assembly Speaker Bob Hertzberg, lacking name recognition but flush with $1.6 million in campaign funds as of Jan. 31, was first to launch his television campaign. The spots have him towering over Los Angeles schools and traffic jams.

John Shallman, a campaign consultant working for Hertzberg, said the early launch was designed to break out of the pack. The campaign then pulled the ads to save money before the final blitz. That accounted for the decision to go off the air between Feb. 19 and Feb. 22, although the ads were back up later in the week.

Like the other candidates, Hertzberg is devoting most of his advertising budget to television, although the campaign also reached out to the Internet more than others.

“In this field, you budget from Election Day backwards,” said Ace Smith, a campaign consultant working for Villaraigosa. “Clearly that’s what we’ve done and that’s what Hahn has done. Hertzberg is taking a different approach.”

L.A.’s cable market further complicates the strategies, with five franchisees serving distinct sections of the city. Shallman said cable ads run as low as $100 per spot, although he noted that putting ads on all five cable providers during prime hours costs more than buying broadcast time.

“Cable TV tends to give you a lot of repetition,” Shallman said. “You’re (accumulating) a lot of repetition with a small number of voters, but you’re reaching a narrower audience.”

Ads for City Councilman Bernard Parks will debut this week, just a few days before the vote, and unlike some of the other campaigns, the spots will air exclusively on broadcast television rather than cable.

That’s a costly proposition for a campaign that has not kept pace with the competition on the fundraising front. A 30-second television spot typically sells for $5,000 to $7,000 during news broadcasts on major network affiliates, among the most popular slots for political advertisements, according to campaign consultants.

A 30-second spot on some of the most popular network programs, such as ABC’s “Desperate Housewives,” costs as much as $65,000 to air. A 15-second ad during less coveted airtime comes in at only hundreds of dollars.

Lacking the money for an extensive broadcast effort, Parks has placed campaign ads in seven AMC movie theaters in Los Angeles and nearby suburbs. The campaign would not say how much the movie trailers cost compared with conventional television advertising.

Hahn’s campaign consultant, Kam Kuwata, said the candidates are having more difficulty reaching voters by television now compared with four years ago. In addition to higher ad rates, campaigns also must deal with fickle viewers who have more tools such as the digital video recorders that allow them to skip over advertising.

“To buy in prime time and get the kind of exposure you need, you have to have the resources and the most clever time buyers,” Kuwata said.

Smith said the increase in advertising costs is magnified by the stations’ use of Nielsen Media Research Inc.’s “people meter” technology, which was rolled out last July and provides a more accurate reading of local viewership. In the past, campaigns tried to have viewers see an ad 10 times a week, but with the more accurate people meter counts, the number of times an ad has to air to reach that threshold has been increased.