A ribald ad campaign for an online dating service has landed TriMet in the sights of a conservative activist group.

The campaign has plastered the acronym DTF -- usually meaning "down to" followed by a rude four-letter word -- on the side of the transit agency's buses. But on closer inspection, the ads indicate couples are down to "farmers market," among other things.

CitizenGO, which hosts online petitions on Christian issues, has targeted the regional transit agency over a series of advertisements for OkCupid. It asks TriMet to change its advertisement policy and remove OkCupid's "distasteful and sexually explicit ads" in an online petition that had nearly 2,000 signatures within hours of its launch Tuesday morning. The effort also directed a steady stream of tweets at TriMet.

In text not included in the statement sent to the transit agency but shown to CitizenGO users, the group said the campaign "promotes lesbian sex, prostitution, drug use, and promiscuity, and it will be viewed by millions, including children, in public spaces."

Some variations of the ad take a political bent, with slogans including down to "filter out the far-right" or "fight about the president." One includes a reference to marijuana use, saying couples are down to "four twenty."

One includes a woman cradling another woman -- bizarrely with an extra pair of hands.

The campaign was created by the Portland advertising agency Wieden+Kennedy's New York office.

TriMet, for its part, is largely barred from rejecting advertisements based on their content.

In 2008, the agency turned away an advertisement opposing hydroelectric dams on the Klamath River, viewing it as political rather than promoting a good or service.

The Karuk Tribe of California and the Friends of the River Foundation, with the aid of the American Civil Liberties Union of Oregon, sued, and the Oregon Supreme Court ultimately found that TriMet cannot reject ads because of their content.

The agency can, however, decline advertisements that are misleading, unsafe, "interfere with TriMet's stated purpose" or could confuse a viewer about who paid for the ad. Ads also carry a disclaimer that TriMet doesn't endorse the content.

This is not the first time the ad campaign has generated controversy. Willamette Week reported in January that a billboard advertising company had rejected one version of the ad, which included a football and two soccer balls in a phallic arrangement.

-- Elliot Njus

enjus@oregonian.com

503-294-5034

@enjus