Swarming around signature-gatherers. Yelling and grabbing clipboards. Pouring a can of soda on a petition.

Such are the intimidating tactics circulators of the Tax and Spending Control ballot initiative petition allege are being used against them by a union-backed group.

On Tuesday, TASC's backers filed a lawsuit against Nevadans for Nevada, the group they allege has overstepped legal bounds to block the petition from getting on the ballot.

"The tactics of the blockers are a clear violation of the law," TASC's executive director, Bob Adney, said at a news conference Tuesday. "They're trying to silence people's voices."

He said the blockers' tactics might prevent TASC from getting the 83,156 valid voter signatures needed to get on the ballot.

Nevadans for Nevada Chairman Danny Thompson denied the allegations.

"We are not harassing them," he said. "All we are doing is exercising our First Amendment rights, just like they are. We don't use physical tactics."

Thompson said the petitioners were failing in their signature-gathering and seeking someone to blame.

"If they were successful in getting signatures, they wouldn't be suing our organization for exercising our rights," said Thompson, who also heads the state AFL-CIO.

The TASC initiative aims to amend the Nevada Constitution to limit the government's ability to spend money.

Its signature-gatherers, posted outside Department of Motor Vehicles offices, grocery stores and other high-traffic spots in the valley, have been the target of a first-of-its-kind effort in Nevada. The petition-blocking group has deployed its own workers at the same locations to hand out leaflets encouraging people to "Read the Fine Print and Decline to Sign!"

TASC's backers, in their lawsuit, allege that the petition-blockers, who they call "hired thugs," did more than hand out leaflets.

The lawsuit accuses the blockers of "illegally impeding and preventing" signatures from being gathered "by intimidation, threats, coercion, violence, restraint, and/or undue influence."

As someone was signing the TASC petition, the lawsuit alleges, blockers approached TASC signature-gatherer Nichole Dickens and put their own papers on top of her clipboard. The blockers stood very close to the signer, talking loudly over Dickens, "thus confusing and intimidating the potential signer," who responded by walking away, the lawsuit alleges.

The lawsuit said such actions are illegal under a Nevada statute that prohibits "intimidation of voters" and that specifically mentions petitions.

"Whether or not we make it (onto the ballot) is not the issue," TASC's attorney, Joel Hansen, said. "The issue is, can petitioners gather in peace, or do they have to be intimidated and harassed?"

The lawsuit seeks a restraining order against the petition-blockers and a six-week extension of the June 20 petition deadline for TASC to make up for the time the lawsuit said the signature-gathering effort has been impeded.

It is scheduled for a Thursday hearing in Clark County District Court.

TASC also filed a complaint with the secretary of state's office calling for criminal charges to be filed against the petition-blockers.

The case echoes another case in which Hansen was involved. Two years ago, Hansen was the lawyer for Nevadans for Sound Government, which sued government entities including the DMV and the University of Nevada for preventing petitioners from gathering signatures on public property.

A judge ruled in the group's favor and gave an extension to the petitions, which aimed to repeal the 2003 tax increase and prohibit public workers from serving in the Legislature. But the two initiatives still did not make the ballot.

"This time it's not government interference, it's government employees' unions," Hansen said. "They are only going after our petition because they don't want this petition (TASC) to succeed."

Adney said: "Now we know the lengths to which the politically privileged will go to try to stop this. It scares them to death. All these unions have a vested interest in growing government, raising taxes and increasing spending."

Adney said the blockers' efforts had caused petitioners to become discouraged and gather fewer signatures or quit, meaning TASC had to spend more money on its signature-gathering.

Thompson said the accusations against Nevadans for Nevada, a coalition that includes several unions including teachers, police and firefighters, were implausible.

He said the group's workers were trained according to a strict set of guidelines that prohibit intimidation.

According to a memorandum provided by the group, the petition "educators" are specifically told not to block anyone's path, follow people or vehicles or "engage in harassing, threatening or abusive conduct."

The memo said, "Communications that are respectful will be more effective in carrying the message."

Thompson said his workers' only objective was to give people the facts before they signed the petition.

The union, which previously filed a lawsuit challenging the way TASC is explained on petitions, contends the fine print of the lengthy proposed constitutional amendment contains hidden provisions that people would not like if they knew about them.

"This is an important public policy issue," Thompson said. "Somebody should be saying, 'Hey, take a look at this before you sign.'"