The Massachusetts Legislature is poised to pass a bill that would dramatically increase disclosure requirements for the huge political action committees known as super PACs, a groundbreaking move that could shed light on the deluge of corporate and labor money expected to flood this year’s race for governor.
The bill would also double the amount of money individuals can give to state candidates from $500 to $1,000 a year, the first change to those limits in 20 years.
With strong support from House Speaker Robert A. DeLeo and Senate President Therese Murray, the legislation, which is expected to clear a key joint committee Wednesday, is likely to pass in the next month, a senior legislative aide said.
The disclosure crackdown, aimed at super PACs as well as nonprofit advovacy groups that fund huge numbers of television ads, would go into effect immediately, should the bill be signed by Governor Deval Patrick. Aides say Patrick expressed support for the concept. The new individual donation limits would not take effect until next year.
The legislation would create one of the strictest and most comprehensive state campaign finance laws in the country. It was designed in response to the array of outside groups that have proliferated since the 2010 Citizens United decision by the Supreme Court, which opened the door to unlimited spending by unions and corporations in political races.
“We are powerless to stop the influx of money to our local races, but we can shed light on those shadowy groups and where their dark money is coming from and how it is being spent,’’ said state Representative James M. Murphy, a Weymouth Democrat and co-chair of the Joint Committee on Election Laws.
The bill is expected to clear that committee Wednesday.
Currently, voters have no way of knowing who or what organization is actually funding many of the ads that saturate the airwaves in the months and weeks leading up to an election. Sometimes all viewers see on the advertisement is the innocuous-sounding name of a super PAC.
Under the proposed law, super PACs will have to disclose their funding sources within seven days of each expenditure they make. The timeline would accelerate to every 24 hours during the eight days before a primary and again eight days before the general election.
In addition, PACs that run television advertisements would have to list in the ad each of the top five “persons or entities” who contributed the most money.
The increased disclosure rules would go into effect in the middle of a gubernatorial campaign that is expected to be heavily influenced by super PAC money. One group has already been created by supporters of Democrat Steve Grossman. Big money donors have also created a PAC in support of Republican Charlie Baker. At the same time,some labor unions are backing a super PAC that has already begun attacking Baker.
Pam Wilmot, executive director of Common Cause Massachusetts, who worked with House and Senate leaders to craft the bill, said the legislation puts Massachusetts in the national forefront of states addressing the torrent of mystery campaign money.
“Other states have done similar legislation,’’ Wilmot said, but when you add up all the elements included in a single bill, “it puts Massachusetts in the leadership in terms of exposing secret money in elections.’’
Opponents of increased campaign disclosure efforts say they violate basic First Amendment principles by not allowing donors to remain anonymous.
David N. Bossie, president of Citizens United, the plaintiff in the landmark Supreme Court case, said in a statement that the bill would have a negative effect on free speech.
“This legislation will chill political speech and no doubt benefit entrenched incumbents,” he said. “More political speech — not less — is good for our democracy.”
The difference between the proposed legislation and the state law now on the books comes on the funding side.
Under current state regulations, super PACs must report how they have spent the money within seven business days of making expenditures. But they only need to report a list of contributors three times: eight days before the primary election, eight days before the general election, and in a year-end report.
And even when the contributors are disclosed, it does not necessarily reveal who the money is actually coming from.
In the final days of the 2013 Boston mayoral race, a mysterious super PAC called “One Boston Independent Expenditure Political Action Committee” spent $480,000 on a major television advertising campaign backing then-candidate Martin J. Walsh.
But the group did not have to reveal its donors until after the election. And when it did, the new information wasn’t very revealing: Its year-end report filed with the Office of Campaign and Political Finance showed a single donor, a group called simply One New Jersey.
The American Federation of Teachers confirmed in late December that it was the donor behind One Boston. The Globe reported at the time that the union gave about $500,000 to One New Jersey, which then gave it to One Boston, which in turn spent it on ads backing Walsh.
Murphy said the new legislation specifically deals with the issues that arose in the mayor’s race. The bill, he said, instructs the head of the Massachusetts Office of Campaign and Political Finance to develop regulations aimed at revealing the original donors who fund those super PACs.
Correction: Because of a reporting error, this story misstated the proposed reporting rules leading up to an election. During the final 10 days before a primary or general election, those reports must be filed within 24 hours after an expenditure is made.