When it comes to the gun issue in American politics, this is ground zero. Almost a year ago, at Columbine High School near here, two students went on a shooting spree, killing 12 of their classmates and a teacher before they took their own lives.

Since then "Columbine" has become shorthand for wanton youth violence, a rallying cry for gun control advocates who see the bloody Colorado incident as a watershed event that will finally break what they consider the iron grip of the National Rifle Association and other anti-gun control groups over Congress and the state legislatures.

But even as guns and youth violence have shot to the top of the public agenda here, the actual political impact of Columbine has so far been relatively limited: Despite the public uproar, the Colorado House recently rejected a package of gun control measures proposed by the state's conservative governor--including requiring background checks for all firearms sales at gun shows.

A grass-roots group formed in the wake of Columbine is now pushing a statewide voter initiative that would put the requirements of the failed state legislation into law by popular vote in November, and advocates are hopeful over early polls showing strong support for the initiative.

Still, the climate in Colorado underscores how difficult it continues to be for gun control advocates to transform general public support for their cause into specific legislation or success for their allies running for office. Although relatively liberal states such as Maryland and Massachusetts have adopted new restrictions on handguns in the past year, most states have relatively limited gun control laws. A package of new national gun controls is hung up in Congress.

According to a study released yesterday by the Open Society Institute, which advocates stricter gun laws, 35 states require no license or registration, 46 set no limit on the number of guns a person can purchase at one time, and seven have no minimum age for buying a rifle.

While Democrats want to make guns a big issue in the elections--when control of Congress and the White House will be up for grabs--Colorado's experience shows that many GOP politicians who might be considered vulnerable on guns have repositioned themselves to make their races less likely to turn on the issue of guns and violence.

One of those lawmakers, Rep. Tom Tancredo (R-Colo.), said the impact of the Columbine shootings in his district has been to "make everyone a bit more sensitive to the issue of guns." But he does not see it as the kind of watershed event that transforms public opinion. "I think the change is marginal," he said.

Some independent analysts agree. "Guns will be a very important variable [in November], but I'm not sure you can win an election on guns alone even in the Columbine district," said Marshall Kaplan, executive director of the Institute for Public Policy at the University of Colorado at Denver. "You are still going to have to package guns with other things."

Historically Colorado has been strong GOP territory, where support for the NRA has not hurt and probably has helped many politicians. Still, the immediate political impact of the school shootings was stark, with public support overwhelming for what Kaplan calls "reasonable gun control initiatives."

A survey last year by the Graduate School of Public Affairs at the University of Colorado at Denver found large majorities of state voters supported new gun control laws, including a requirement for background checks on all firearms sales at gun shows.

On the other hand, the same Colorado survey showed that a 58 percent majority agreed with the statement that "new gun control laws aren't necessary if we would just enforce the current laws."

A recent Washington Post-ABC News survey suggested a similar phenomenon nationally: A slight majority of 53 percent said that stricter enforcement of existing laws, rather than new laws, was the best way to reduce gun violence.

Against the backdrop of this apparent contradiction, both sides are jockeying for the advantage in Colorado and elsewhere. The debate over tougher enforcement and new gun control laws "is the way the issue will be joined in [congressional] races and nationally," said James Jay Baker, the NRA's chief Washington lobbyist.

In Colorado, Bill Owens, a conservative GOP governor who was widely viewed as a gun control opponent, responded to Columbine by calling for passage of gun show background checks and other measures.

But in the months since then, the Colorado House rejected the gun show law and two other measures supported by Owens. The opponents included state Rep. Don Lee, a conservative Republican whose district includes Columbine High School. At this point, Lee does not appear in danger of defeat in the heavily Republican area.

"I don't really think that it's changed a lot of people's opinions," Lee said of the Columbine shootings. "I don't think people will take one part of one issue and determine their vote on that one thing alone."

Still, Tancredo has moved to limit any potential liability from guns. The freshman lawmaker is a conservative, the former head of a libertarian think tank and a self-proclaimed "Second Amendment advocate" whose home is about six blocks from Columbine High School in the sprawling Denver suburbs.

Last year, Tancredo voted with a majority of House Republicans for an amendment to a gun control measure that critics charged crippled an attempt to close the "gun show loophole," which allows vendors who are not federally-licensed to sell firearms at gun shows without a background check of the purchaser. The federal legislation, which remains stalled in Congress, was similar to the Owens-supported measure that was killed by a Colorado House committee.

This year, Tancredo appears to have changed his mind, endorsing the proposed Colorado ballot initiative. "It's a relatively reasonable approach," he said in an interview.

Meanwhile, he has returned a $1,000 check from the NRA and vowed not to accept contributions from organizations on either side of the gun issue. In his 1998 campaign, according to federal election records, Tancredo accepted $9,500 from the NRA and another $500 from the Gun Owners of America.

Ken Toltz, Tancredo's Democratic opponent, dismisses Tancredo's endorsement of the gun show ballot initiative as the stance of a politician "who is out of touch with what his job responsibilities are."

"He had an incredible opportunity last summer if he would have just stood up on the House floor and said this is something we have to do," said Toltz, who owns a chain of dry-cleaning establishments and is making his first run for public office. "If he had, we wouldn't be here with a citizens' ballot initiative. It would have been done."

Tancredo's endorsement of the gun show initiative has angered some gun control opponents in the state, costing him their support, but it may make him less vulnerable to attacks by Toltz and other advocates of new gun control laws.

Like every freshman member, Tancredo is most vulnerable in his first campaign for reelection, said Arnie Grossman, a Democratic consultant and co-president of SAFE Colorado, the grass-roots organization pushing the ballot initiative. "On the other hand," he said, he gave Tancredo credit for his support of the initiative. "He has listened," Grossman said. "Is he listening to us? Probably not. I think he's listening to the people of his district."

"I think he has taken [gun control] off the table," added John Head, a Republican lawyer and SAFE Colorado's co-president.

Still, Toltz intends to make guns an issue this fall. He said he will try to portray Tancredo as unresponsive and out of step with his constituents on that and other issues.

"I don't know that when people go to the polls in November that this issue is going to be the one issue that is going to make them pull the lever," Toltz said. "But I do know that in Colorado they're looking for action on a range of fronts and the government and the political leaders need to show the urge to tackle those. This is important to everyone in Colorado. This is the safety of our kids."

Staff writer Peter Slevin contributed to this report.