It's official: Arizona Sen. John McCain will skip Iowa.

"I will not conduct any organized campaign effort . . . nor will my campaign be spending money on advertisements, staff or organizational activities," McCain wrote in a letter yesterday to Iowa Republican Party Chairman Kayne Robinson. McCain still plans to attend debates in Iowa on Dec. 13 and Jan. 15 but said he could not afford to actively compete in the state's Jan. 24 caucuses while simultaneously mounting efforts in New Hampshire and the handful of contests that quickly follow.

"My decision not to establish a campaign organization in Iowa is based solely on the compressed nature of the primary schedule and the increasing influence of big money on the nominating process," McCain wrote.

McCain aides had long indicated he was likely to pass on Iowa and instead concentrate resources on New Hampshire on Feb. 1 and South Carolina on Feb. 19, hoping to build momentum to carry into the primaries that will likely decide the nomination in early March. More recently, with his poll ratings going up, McCain had suggested he might play in Iowa.

Iowa GOP spokesperson Ann Dougherty said state Republicans were not surprised by McCain's decision not to compete, but added: "For the sake of the caucuses, we hoped he would have done more. It's interesting because he cites big money as the problem and in Iowa you can run a highly effective campaign at the grass-roots level. That's part of the beauty of the caucuses."

Ad Accused of Being 'Attack Surrogate'

Republican Steve Forbes's campaign yesterday filed a complaint with the Federal Election Commission charging that a new television ad urging him to refrain from attacking his rivals amounted to an illegal $100,000 contribution to GOP frontrunner George W. Bush.

The ad is being run by the Republican Leadership Council, a group of Republican moderates with close ties to Bush's campaign. Twenty-eight of 35 top RLC officials are leading Bush backers, according to the Forbes campaign. In his complaint, Forbes campaign manager William Dal Col called the group an "attack surrogate" for Bush.

McCain, another Bush rival, also blasted the group yesterday, arguing in a letter to the RLC chairman that the ads should be pulled from the air because they use "unregulated campaign contributions to fund an advertising campaign directed against a single candidate."

The RLC ad in Iowa was meant to be a preemptive strike against new Forbes ads, warning Forbes "if he doesn't have anything nice to say, he shouldn't say anything at all." But Forbes scrapped plans to criticize Bush in his ads, running instead with issue-based spots. The group's executive director said he did not review the RLC ad with any Bush backers on his board or with the campaign.

Staff writer Susan B. Glasser contributed to this report.

CAPTION: Sen. John McCain.