(CNN) A mysterious PAC that emerged earlier this year in the US Senate race in North Carolina and propped up insurgent Democratic State Sen. Erica Smith in the Democratic primary was backed by a group aligned with Senate Majority Leader Mitch McConnell, a Federal Election Commission filing reveals.

The Senate Leadership Fund funneled nearly $3 million into the Faith and Power PAC, according to the FEC filing. They spent more than $2.4 million of it on a well-known media buyer Neylan and Partners, which has been affiliated with Republican campaigns in the past. The ads in support of Smith began appearing in the state in recent weeks ahead of the March 3 primary in North Carolina and touted her support for liberal policies like "Medicare for All" and the "Green New Deal."

"Who's the Democrat for US Senate endorsed by progressives and unions? Erica Smith," the ad's narrator said. "Who's got the courage to vote for 'Medicare for All'? Erica Smith. The number one supporter of the Green New Deal? Erica Smith again."

Smith, a relatively unknown state senator who has reported just around $200,000 in her own campaign coffers, is running against veteran and former state senator Cal Cunningham who won the endorsement of the Democratic Senatorial Campaign Committee and has been considered as a serious challenger to incumbent Republican Sen. Thom Tillis. Cunningham lost a Democratic primary in 2010 against Elaine Marshall.

Cunningham's campaign spokeswoman Rachel Petri tweeted that it was "hilarious that Washington GOP is patting itself on the back for its $3 million admission that @SenThomTillis is their weakest incumbent and they don't want him to run against @CalforNC."

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