But who asked for this? Where is the upsurge in interest in decriminalizing prostitution? Four years ago a similar measure was rolled out in freethinking Berkeley, to much national ballyhoo, and it lost by 63 percent. Why would anyone think it would be popular in San Francisco now?

"I heard rumors of that," said David Chiu, a committee member and supervisorial candidate in District Three, who voted against the measure. "But the issue never came up."

No worries. It will.

"I think this was a real litmus test across the city on where these guys want to go," said political consultant David Latterman, who is advising several moderate campaigns and is working for Claudine Cheng's supervisorial run in District Three and Emily Murase's bid for school board. "This is what they stand for. It shows how incredibly out of touch they are."

Certainly there is nothing wrong with the concept. This is San Francisco, after all, and it probably wouldn't be difficult to get support for a measure that would allow prostitutes to report crimes like assault or rape without fear of prosecution.

"I don't think any of us wants to see sex workers put in jail," said Scott Wiener, a past president and current member of the DCCC. "And I don't have any problem with the Democratic Party getting out in front of a controversial issue. This is just a bad idea. For one thing, it could jeopardize investigations into human trafficking and pimping."

Better get used to that politically loaded term, "human trafficking." Proponents of the measure, like District Nine supervisor candidate David Campos, a member of the committee who voted for K, disagree with the characterization. (McGoldrick's office, on vacation, did not respond to a request for comment.)

"In no way was I condoning human trafficking," said Campos, a member of the police commission. "My understanding is that they are two different issues."

But the measure clearly states that law enforcement agencies are not to use funds to target traffickers if there is any use of racial profiling. It also demands that the city not support any program that "forces sex workers into re-education programs."

So Measure K proponents believe that racial profiling is the greatest concern when women are being forced into prostitution? That re-education programs should be discouraged, not encouraged?

When San Franciscans are deeply concerned about violent crime, a measure that seeks to decriminalize prostitution doesn't sound like a winner.

That may be one reason why the newly elected chairman of the DCCC, Aaron Peskin, voted against the measure. (Peskin was out of town and unavailable for comment.) And why candidates like Eric Mar, who is running for supervisor in McGoldrick's district, wasn't able to spare a moment to comment on his vote in favor of K.

"He's extremely busy today," said Mar's brother, Gordon. "He won't be able to get back to you."

Even Measure K opponents recognize it's a loaded issue.

"Personally, I strongly believe consenting adults can do what they want to do," Chiu said. "But as a former prosecutor, I know that in sex trafficking there are unconsenting adults and minors, and there is not enough protection for them."

I predict those who voted for K will find it very hard to argue with that. If they didn't get the message before, it should be sinking in now. This is the kind of touchstone issue that can make - or break - an election.

Clarification: The above column incorrectly reported that Supervisor Jake McGoldrick is the sponsor of Measure K, a Nov. 4 ballot initiative that would decriminalize prostitution in San Francisco. McGoldrick supports the measure, but it is being primarily advocated by the Erotic Service Providers Union.

C.W. Nevius' column appears Tuesday, Thursday and Saturday. E-mail him at cwnevius@sfchronicle.com.