(CNN) - A conservative group announced Friday that its members spent $2 million in Senate races in the fourth quarter of 2013, roughly half of which went to support Senate Minority Leader Mitch McConnell's arch-conservative primary challenger.
The Senate Conservatives Fund said members invested nearly $1 million in the primary race to oust McConnell and nominate tea party challenger Matt Bevin.
McConnell, however, has a hefty war chest. While he hasn't announced spending or fundraising figures for last year's fourth quarter, his campaign had nearly $10 million cash on hand as of the end of September.
The SCF helped raise and spend about $0.5 million in Mississippi against incumbent GOP Sen. Thad Cochran, who is facing a primary challenge from state Sen. Chris McDaniel.
In another Republican primary challenge, SCF members spent just over $100,000–either directly or through SCF's own efforts–backing challenger Milton Wolf against GOP incumbent Sen. Pat Roberts of Kansas.
"The Republican establishment in Washington may spend hundreds of millions against conservative candidates this year, but the grassroots aren't going down without a fight," SCF Executive Director Matt Hoskins said in a statement.
The rest of the $2 million goes toward SCF's endorsed candidates in the open Nebraska Senate race and in Louisiana, where Democratic incumbent Sen. Mary Landrieu is defending her seat.