The conservative group Heritage Action -- the political arm of the Heritage Foundation -- announced Monday that it will oppose Janet Yellen's nomination as Federal Reserve chairwoman and will make it a "key vote" by which it will score members' conservatism.

Heritage has said it fears the Fed has become more political as it has taken on a more active role following the recent financial crisis and subsequent legislation ramping up oversight on the banks.

Yellen is expected to be  confirmed and got the support of three GOP senators in the Senate Banking Committee last week.

She did earn the opposition of one Democrat -- Sen. Joe Manchin (D-W.Va.) -- but needs only 50 votes after Senate Democrats last week voted to adjust the threshold for presidential nominees.

Democrats currently have 55 senators in their caucus.