PHOENIX  — A new lawsuit is making another stab at overturning a key provision of Arizona’s decade-old Clean Elections law.

But this one hopes to stop the system dead in its tracks immediately, a move that, if successful, could affect the outcome of this year’s primary where early voting already has started.

The 1998 law allows  — but does not require  — candidates for statewide and legislative office to get public funding.

That measure was approved by voters despite objections of several business groups  — groups that have traditionally financed campaigns through both personal donations of executives and political action committees.

Attorney Clint Bolick of the Goldwater Institute said the law is unconstitutional because it seeks to equalize funding: If a privately financed candidate collects more than the allocation for the one running with public dollars, the latter is given more cash.

And Bolick said the inequity is even worse: If an independent group campaigns for a privately funded candidate  — even over the objections of that person  — the publicly funded foe gets more money. Yet an independent expenditure made on behalf of publicly financed candidates does not provide dollars for the privately funded foe, or even offset the matching funds given to the person running with public dollars. Bolick, representing some incumbent and would-be legislators running with private donations, said all that interferes with their constitutionally protected right of free speech. His lawsuit asks U.S. District Court Judge Roslyn Silver to block the Clean Elections Commission from providing more matching funds for publicly financed candidates while she reviews the constitutionality of the law. That would allow privately financed candidates to spend as much as they want between now and the Sept. 2 primary  — and the Nov. 4 general election  — without fearing that their actions would provide additional dollars for their publicly financed foes to respond. But Bolick said that’s too bad.

“They shouldn’t accept government funds for their campaigns to begin with,” he said.

And Bolick said they’ve already had a built-in advantage.

Those public funds do not come automatically: Candidates must first gather a set number of $5 donations to prove they have a base of support.

This is actually the second federal court lawsuit challenging the matching fund provision.

In 2005, U.S. District Court Judge Earl Carroll threw out constitutional complaints about the law. He ruled that the government can adopt rules designed to abolish even the appearance of corruption in the political process.

But the 9th U.S. Circuit Court of Appeals, while not overturning that decision, sent the case back to Carroll to reconsider.

Attorney Tim Keller of the Institute for Justice, who is handling that case, said no date for a new trial has been set.