WASHINGTON - The upbeat pre-Christmas tone of the 2008 presidential campaign is about to shift.

While a frenzy of campaign activity in Iowa by labor unions and other special-interest groups began this month, with advertising carrying more or less positive messages about the candidates, federal election reports show that several groups not officially affiliated with the contenders are ready to launch attack ads and mailers across the state, directed at least at various Democrats.

Over the weekend, the American Federation of State, County and Municipal Employees filed documents with the Federal Election Commission reporting it will spend $40,755 on a mailing opposing Sen. Barack Obama (D., Ill.). AFSCME is one of three major groups in Iowa promoting Sen. Hillary Rodham Clinton (D., N.Y.).

A political action committee called Democratic Courage, run by a supporter of former Sen. John Edwards, has reported it will spend about $20,000 on a television ad opposing Clinton. The group had announced plans this year to run "hard-hitting, creative ads in key primary states highlighting why Sen. Clinton should not be the first choice of voters who want to end the war in Iraq, fight global warming, win universal health care - or beat the Republicans."

The group, which has specialized in low-cost ads designed to attract media attention, has also placed a video critical of Obama on its Web site. In that ad, "Santa Barack Obama" is shown delivering lumps of coal to Iowa voters in the form of votes he cast that the PAC opposed.

Two conservative groups have also gotten into the act, announcing they will pay for ad campaigns in the week before the Jan. 3 caucuses.

A political action committee affiliated with Republican Alan Keyes declared its intention to spend $39,000 on phone banks and mailers opposing Clinton. And a PAC called RightMarch.com, which describes itself on its Web site as a conservative group that targets liberal Republicans and Democrats for defeat, reported it would spend $16,465 on mail opposing Clinton.

The FEC requires that within 20 days of an election, independent groups file reports any time they spend more than $1,000 to support or oppose a candidate.

The only other papers filed with the FEC over the weekend were for mailers promoting Democrat Bill Richardson. Whether they help the New Mexico governor's campaign will depend on what the Democrats who receive them think of the group that footed the $9,000 bill: the National Rifle Association.