Quick Rorschach test: I show you a picture of a clown.

You answer: Boston City Council.

Small wonder. The council's most recent humiliation comes from the desk of Marty Keogh, a staffer for Councilor Peggy Davis-Mullen.

Keogh has a well-deserved reputation in City Hall as a modern-day Dick Tuck, the legendary master of political dirty tricks. In his latest, Keogh fired off nasty e-mails to two other councilors and got a letter published in this newspaper, all under the nom de plume of Susan Holmes. Keogh's mistake? The wizards from the city's Management Information Services Department were able to track down the e-mails to a specific time and a specific computer.

Turns out it was Keogh's computer.

It didn't stop there, however. The e-mail caper preoccupied City Hall for a week. Councilors called the district attorney, trying for a criminal prosecution. They pushed for public hearings. They talked about it incessantly.

Sometimes it seems as if squabbling is the council's drug of choice. Even as councilors swear it off, giving nice speeches about the critical business of the city and the need for the body to be united, they can't seem to help themselves. Opportunities to take a shot at another councilor just can't be passed up.

It's a sad picture, one that brings ridicule on the council, making it seem frivolous and irrelevant.

It's also an inaccurate picture. The Marty Keoghs of the world aside, the council is populated with largely decent people who have a surprisingly large effect on the daily business of the city.

John Harrington's recent surprise announcement that he was selling the Red Sox is seen by many as a product of the council's adamant opposition to eminent domain land takings for a new ballpark. So too the council played a role in the administration's recent loss of nerve in the face of a teachers strike. A vast majority of the body sided with the teachers union, meaning that Menino had weak political cover for his efforts on school reform.

The council also injected itself into negotiations over the city's draft of the Municipal Harbor Plan. That plan, if approved by the state, will guide development on the South Boston waterfront.

A few weeks ago, 10 of the body's 13 members co-sponsored a resolution written by Councilor Maura Hennigan that opposed the development plan. Two days ago, beaten up by labor unions and the Menino administration, councilors caved, ultimately voting 7-5 for a resolution that supported the plan.

Admittedly, sometimes it seems as if the council is like New England weather: If you don't like a vote, wait an hour.

Yet, even on the Municipal Harbor Plan, the council was influential. Its momentary revolt was a wake-up call to the administration and the Pritzker family, which owns the key parcel of land known as Fan Pier. If the council had stuck with its opposition, chances for the plan's approval would have been hurt. Conversely, the council's new position undoubtedly makes Environment Secretary Robert Durand's decision an easier one.

For better or worse, the council played a role in each of these controversies.

But it is on the most local of issues where councilors really have an effect.

Councilor Mike Ross, for example, discovered that a large apartment building on Mission Hill was built on city-owned land. Large rent increases had to be rolled back because of long-forgotten agreements with the city that limited rents.

When Councilor Hennigan suggested the city install speed bumps to slow down cars racing through residential neighborhoods, the public works department told her they were illegal. After some research and heavy lobbying, she finally persuaded the city to test out raised crosswalks (which are no more than speed bumps by a different name) in three different neighborhoods. They're being installed this fall.

Roslindale's Fallon Field, a filthy magnet for late night drinkers, is now quiet and safe, thanks to Councilor Dan Conley organizing a community-wide meeting to clean up the park. So too with Hobart Park in Brighton. After a three-year effort led by Councilor Brian Honan it has received over $250,000 for landscaping, new fencing and two new playgrounds.

The city's mobile mammography van is a direct outgrowth of an idea by several female councilors worried about the number of women who were not being screened for breast cancer. Now in its first year of operation, the van sees 15 to 20 women a day, most of whom do not  have access to conventional medical services.

Things like this happen all of the time. None of them, of course, makes it to the front page or the nightly news. But they all matter.

It leads to an odd contradiction. Councilors believe they are doing good work - and they are right. But too often those good deeds are buried by things both petty and unprincipled.

Tom Keane writes every Friday for the Herald. He can be reached at tomkeane@tomkeane.com.