In April, Moms Against Guns had a humble request: one affordable billboard advertising its petition for stricter gun laws.

Flash forward three months, and the Philadelphia-based advocacy group now has 27 billboards citywide, with at least six more on the way.

The billboards will stay up through November's elections - just long enough, the group says, for voters to elect candidates willing to crack down on illegal guns.

It's all part of what founder Lynne Honickman called a viral campaign.

"Everybody has a power: the power to vote," Honickman said. "Not until the general public says 'enough' will the politicos do their duty."

The group is working on getting 50,000 signatures for a petition on its Web site (http://www.momsagainstguns.org) urging state lawmakers to pass tougher gun laws. The petition has nearly 4,500 so far.

The billboards come free from Clear Channel Outdoor Philadelphia and Interstate Outdoor Advertising, two locally based firms.

"We didn't think a billboard was going to make a difference," said Drew Katz, chief executive officer of Interstate. "Thirty billboards might make a difference."

The slew of billboards reflects a sense of urgency as gun violence continues to claim lives.

As of yesterday, there were 175 homicides this year in the city. Of those, 138 were committed with handguns, two with rifles and four with shotguns, said Lt. Frank Vanore, a police spokesman.

"It's obvious that guns on the street are a major, major problem," Vanore said.

He cited another statistic: Over the last year, three police officers were killed and several others were shot. It is becoming "very, very dangerous to face" gun-toting criminals, he said.

The campaign by Moms Against Guns has the support of Mayor Nutter, who has tried to pass tougher gun laws, while Harrisburg legislators have bristled.

Yet, as Honickman acknowledged, the campaign is preaching to the choir. "The inner city knows its problem," she said, noting strong pro-gun sentiments across much of the state.

Honickman would like to raise billboards outside Philadelphia. "We are statewide," she said, "but whether someone is going to give us billboards is another issue."

In the meantime, Honickman said she hoped the petition would get the legislature's attention.

"We need to fight this fight," she said. "It's an uphill fight, which it shouldn't be."