AUGUSTA — The conservative Maine Heritage Policy Center and Indiana-based James Madison Center for Free Speech have filed a suit in federal court saying Maine’s Clean Elections law is unconstitutional.

The groups on Friday said the law, which provides public campaign funding for qualified candidates for governor and Legislature, infringes on First Amendment free speech rights.

Several others, including some current and former legislators, have signed on as plaintiffs in the suit.

A group called Maine Citizens for Clean Elections defends the law, saying it’s worked effectively for more than a decade to combat the influence of big money in Maine elections.

Arizona has a similar law. A federal judge earlier this year invalidated a key portion of that law dealing with distribution of matching funds.