Maine Attorney General William Schneider’s office said Monday he would not be joining counterparts in 22 other states and the District of Columbia in a legal gambit to limit the effect of the U.S. Supreme Court’s 2010 Citizens United decision, which lifted many restrictions on corporate campaign spending.

The Associated Press reported Sunday that 22 states led by New York had signed on to a brief asking the court to allow Montana to continue to restrict corporate expenditures in state elections. The Supreme Court’s reaction will be closely watched because it will likely determine the degree to which states can regulate political donations in the wake of Citizens United.

Schneider, who is seeking the Republican nomination for the U.S. Senate seat to be vacated by Olympia Snowe, received a request to support the brief earlier this month and declined, according to his office.

“Attorney General Schneider did not do so because he believes that the Citizens United decision, which is the law of the land, correctly protects First Amendment rights of American citizens to engage in politics,” said his special assistant, Brenda Kielty.

Kielty also noted that “a majority of state attorneys general did not join the brief”.

In Citizens United v. Federal Election Commission, the court ruled that government restrictions on independent political spending by corporations and unions violated the First Amendment.

According to the Associated Press, the states backing Montana were New York, Arkansas, California, Connecticut, Delaware, Hawaii, Idaho, Illinois, Iowa, Kentucky, Maryland, Massachusetts, Minnesota, Mississippi, Nevada, New Mexico, North Carolina, Rhode Island, Utah, Vermont, Washington and West Virginia.

A number of Democratic legislators are trying to pressure Schneider to reverse his stance. Rep. Jon Hinck, D-Portland — who is also running for the U.S. Senate — sent a letter to Schneider April 18 signed by 47 Democratic lawmakers asking him to support an initiative to ask the U.S. Congress to introduce a constitutional amendment that would overturn the Supreme Court’s decision. Kielty said the letter remains under consideration.

Another Portland Democratic representative, Diane Russell, began circulating a petition Monday that asks Schneider to sign on to the brief in support of Montana. “This is an opportunity to revisit the remarkable impact that Citizens United has had on our elections system and our democracy and provide the Supreme Court with an opportunity to fix what they broke,” Russell said.

Montana law has banned corporate contributions in state contests since 1906, a reaction to the extraordinary influence of the Butte-based Anaconda copper company in the state’s affairs. Maine, by contrast, allows corporations to contribute to political campaigns and, even before Citizens United, placed no limits on contributions to political action committees.

Anthony Corrado Jr., a professor of government at Colby College and one of the nation’s leading experts on money in politics, said the Montana case has dim prospects. “I find it highly unlikely that the Supreme Court is going to reverse itself, but instead is going to find the (Montana) state statute is to be struck down as not being in compliance with constitutional law,” he said.