Liberal dark money has poured into states with competitive Senate races this election cycle despite Democrats repeatedly chastising dark money from Republicans in past election cycles.

Majority Forward, a 501(c)(4) "social welfare" nonprofit" that hides its donors, has spent more than $40 million this cycle aiding Democratic candidates in nine states and is by far the biggest dark money spender for the midterms, the Center for Responsive Politics reports.

Majority Forward was incorporated in June 2015 by Marc Elias, a partner at the D.C. office of the Perkins Coie law firm. Elias previously acted as Hillary Clinton's top campaign lawyer and represents a number of Democratic politicians and organizations, including the National Democratic Redistricting Committee, a group founded by former attorney general Eric Holder that is backed by former President Barack Obama.

The group is closely linked to the Senate Majority PAC, a committee affiliated with Sen. Chuck Schumer (D., N.Y.). Majority Forward and the Senate Majority PAC have shared staff and office space.

Majority Forward's spending has skyrocketed this cycle by more than $30 million from the 2016 election cycle. The group aired nearly 30,000 advertisements between Sept. 18 and Oct. 15 opposing Republican candidates and supporting Democrats for the midterms.

The group is steering its focus to a handful of tight Senate races.

Majority Forward has spent $7.4 million against Republican representative Marsha Blackburn, who is running for Senate against Democrat Phil Bredesen in Tennessee; $9 million in the Florida Senate race, half of which was in opposition to Republican Senate candidate Rick Scott; and added at least $2 million against Republican candidates in Arizona, Indiana, Missouri, Montana, and Nevada.

The Center for Responsive Politics notes that the group teamed up with VoteVets, a progressive veterans group, for two of its ads attacking Republicans.

Majority Forward and VoteVets also teamed up earlier this cycle to defend Sen. Tammy Baldwin (D., Wisc.), who regularly attacks dark money in politics, over her handling of the Tomah VA controversy in Wisconsin.

Elias, who incorporated the group, in 2015 was brought in to help Baldwin following the controversy, and his law firm was paid $90,000 for crisis control that year. Majority Forward then ran ads this cycle defending Baldwin, the Washington Free Beacon previously reported.

The Senate Majority PAC has additionally passed millions of dollars to VoteVets this election cycle.