President Obama led Democrats in a coordinated attack against the U.S. Chamber of Commerce on Thursday, painting the business lobby as a corporate interest standing against open elections and U.S. workers.

Obama criticized the Chamber for opposing campaign finance reform legislation that would require corporations and unions to disclose the names of those making donations for political ads. He did so as The Associated Press reported the Chamber is airing $10 million in ads this week, most of which attack Democrats and their policies.

“Just this week, we learned that one of the largest groups paying for these ads regularly takes in money from foreign corporations,” Obama said Thursday at a rally in Maryland.

“So groups that receive foreign money are spending huge sums to influence American elections, and they won’t tell you where the money for their ads comes from.”

The attack by Obama follows a report by the liberal blog ThinkProgress suggesting the Chamber impermissibly accepted and spent foreign donations to support its political activities, an illegal practice the Chamber has vehemently denied engaging in. It’s the latest in a series of skirmishes between Democrats and the Chamber, which have feuded repeatedly over the years.

Sen. Al FrankenAlan (Al) Stuart FrankenGOP eying 'blue slip' break to help Trump fill the courts Overnight Regulation: FTC launches probe into Equifax | Dems propose tougher data security rules | NYC aims to slash greenhouse gas emissions | EPA to reconsider Obama coal ash rule Overnight Cybersecurity: Kaspersky to testify before House | US sanctions Iranians over cyberattacks | Equifax reveals flaw that led to hack MORE (D-Minn.) wrote the Federal Election Commission (FEC) earlier this week to ask for a probe into the Chamber's funding, while a number of Democrats sought to tie the Chamber to their broader attack against Republicans, whom they accuse of protecting corporate interests.

“Republicans voted 11 times in four years to protect tax havens for corporations that ship American jobs overseas, and now the U.S. Chamber of Commerce is possibly using funds from foreign interests and foreign governments to influence the elections,” said Nadeam Elshami, a spokesman for House Speaker Nancy Pelosi (D-Calif.).

It’s possible that the Chamber could find itself on the receiving end of a negative advertising blitz by Democrats, as well. “Stay tuned,” said one party official about the possibility of ads demonizing the group.

The Chamber, for its part, scolded Democrats for their attacks while doubling down on their arguments that Obama’s policies were cutting off economic growth.

“This coordinated effort is a desperate attempt to silence those who support free enterprise and a diversion from their lack of progress on job creation,” said Tita Freeman, the Chamber's vice president for communications.

Tom Donohue, the Chamber's president and CEO, said Thursday during a speech in Iowa that Obama’s administration is imposing regulations that are “suffocating the entrepreneurial spirit,” according to a report in Bloomberg. He said the Chamber might challenge the Obama administration's new regulation on businesses in court.

“The regulatory impact on the business community is pervasive, insidious and needs to be exposed,” he said.

The tense relationship between the Chamber and Democrats that’s now playing out dates at least to the last election, when Sen. Chuck SchumerCharles (Chuck) Ellis SchumerSenate Dems hold floor talk-a-thon against latest ObamaCare repeal bill This week: Senate wrapping up defense bill after amendment fight Cuomo warns Dems against cutting DACA deal with Trump MORE (D-N.Y.), at the time the leader of Senate Democrats' campaign efforts, accused the group of acting as an arm of the Republican Party.

The White House and Chamber found middle ground early after Obama took office, when the group endorsed the president's $787 stimulus bill. But since then, Democrats and the Chamber have clashed on a variety of issues — from climate change legislation to healthcare and Wall Street reform to a new proposal to regulate campaign finance.

It’s within the framework of that campaign finance bill in particular that Democrats have sought to frame the Chamber as a villain.

“Americans have a right to know if these contributions are tied to outsourcing of jobs,” said Elshami. “Democrats have voted to end those loopholes and keep American jobs here and for full disclosure of these campaign donations, while Republicans and their allies stood in the way.”

The Democratic push is just the latest effort to gain political traction in a difficult election cycle by way of negatively highlighting opponents. The president and Democrats had previously harped on House Minority Leader John BoehnerJohn Andrew BoehnerSpeculation mounts, but Ryan’s job seen as safe Boehner warns Trump: Don't pull out of Korea-US trade deal GOP Rep: Ryan wasting taxpayers dollars by blocking war authorization debate MORE (R-Ohio), the lawmaker who would likely become Speaker of the House if the GOP reclaims the majority, with mixed results.

Obama and other Democrats have repeatedly slammed Republicans for having held up the campaign finance bill, known as the Disclose Act, that is meant to counteract the effects of a Supreme Court ruling earlier this year freeing up corporate and labor spending in the election.

That decision allowed the Chamber, along with different groups headed up by top Republican strategists Karl Rove and Ed Gillespie, to become key figures in the 2010 elections, according to David Plouffe, Obama's 2008 presidential campaign manager.

“They are becoming the central financial actors in this election,” Plouffe said Thursday at a pre-election briefing for reporters. “It's happening more on their side than on ours.”

But the Chamber's support this cycle hasn't been entirely monolithic on Republicans' behalf, either. Rep. Walt Minnick (D-Idaho), a top target for the GOP this fall, got the Chamber's backing for his reelection, and the group also weighed in on behalf of Democratic Gov. Joe ManchinJoseph (Joe) ManchinGOP sees fresh opening with Dems’ single payer embrace Trump steps up courtship of Dems The Hill's 12:30 Report MORE (D), who's running against Republican John Raese in an increasingly competitive Senate race in West Virginia.