IT started as a small group of American mayors worried about gun violence. It has since grown into a vociferous national organisation that has challenged the powerful US gun lobby and boosted speculation about the presidential prospects of Michael Bloomberg, the mayor of New York.

The latest recruit to Bloomberg’s coalition of Mayors Against Illegal Guns is Patricia Tucker, the widow of a North Carolina sheriff who was shot in the face by a teenager on probation for an earlier offence. He was found to have bought a shotgun from a dealer who allegedly should have refused the sale.

Tucker appeared last week in a new advertising campaign aimed at Congressional allies of the National Rifle Association, the defender of American gunowners’ rights. Bloomberg’s assault on one of Washington’s most powerful lobbying groups has marked him out as both a target for right-wing critics and as a bold, energetic campaigner whose immense personal wealth might enable him to side-step the traditional primary-filled path to the White House.

As the billionaire founder and majority owner of the Bloomberg media empire, the mayor is considering spending $1 billion of his personal fortune on an independent campaign in the 2008 White House race.

Bloomberg played it cool at a succession of New York events last week, shying away from “off-topic” nonmunicipal questions. Asked if he thought he would make a good president, he replied: “I’ve got a job. I just want to be a good mayor.”

Yet there has been an unmis-takeable national echo to the antigun, pro-environment and other municipal initiatives unveiled by a mayor whose popularity in New York – where his approval rating is currently 74% – could stand him in good stead for a shot at becoming America’s first Jewish president.

Since succeeding former mayor Rudolph Giuliani a few weeks after the September 11 terrorist attacks, Bloomberg, 65, has cut city property and income taxes, increased spending on schools and has generally been “running like a [battery-oper-ated] bunny”, said Maurice Car-roll, director of the Quinnipiac university polling institute. “But what is he running for?”

He still lives a billionaire life-style, with weekend excursions by private jet to his Bermuda estate, but most days he travels to work on the subway. While many New Yorkers still admire Giuliani for his handling of 9/11, there is a strong feeling that Bloomberg has done more to improve the city’s quality of life.

The challenge for Bloomberg, a fiscal conservative with liberal leanings on social issues, has been to find an issue that might resonate around the country as strongly as Giuliani’s 9/11 appeal – and which might help the rest of America overcome its likely resistance to too many New York politicians in the race.

It was in April last year that Bloomberg first called a group of 15 mayors to a summit on gun violence at Gracie Mansion, his Manhattan residence. The group has since expanded to represent 225 cities around the country, providing the mayor with a ready-made national network of potential political allies.

Bloomberg caused uproar in gunowning circles last year when he sent undercover agents to conduct sting operations against 43 dealers in five states who were suspected of selling guns illegally. The mayor cited studies that more than 90% of illegal handguns used in New York crimes originated with out-of-state dealers, but the NRA dubbed him a “national gun control vigilante” and depicted him on the cover of a gun magazine as a sinister-looking octopus.

The battle has since switched to Republican-sponsored legislation that Bloomberg’s group opposes because it allegedly restricts police access to gun sales data. The Republican congressman who introduced the legislation has received more than $40,000 in campaign contributions from the NRA.

Last week a lorry carrying billboards publicising Bloomberg’s group drove around Washington with the message: “Why is Congress soft on crime?”. Tucker tearfully urged television viewers to “ask Congress to protect police officers, and not criminals”.

Robert Shrum, a Democratic strategist and sometime adviser to Tony Blair, said Bloomberg’s gun control position might “doom him” in any two-way race in heartland states such as Missouri. But in a three-way contest, Shrum added, he might still emerge the winner with as little as 35% of the vote if the pro-gun vote split evenly between Republicans and Democrats.

Shrum believes that Bloomberg will decide next February whether there is an exploitable gap between the main party nominees. If the Democrats choose either Hillary Clinton or Barack Obama – both popular with liberals – then moderate Democrats may get nervous and be open to an alternative.

If the Republicans choose Giuliani or Fred Thompson, the conservative Hollywood actor, disaffected Republicans might also be ready to jump ship.

Mark Green, Bloomberg’s defeated New York opponent in 2001, said the mayor was being clever by being coy. “He’s showing some leg on running for president,” said Green, “but he’s not yet doing the full striptease.”

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