The American Conservative Union has filed a complaint against Barack ObamaBarack Hussein ObamaKrystal Ball tears into 'Never Trump' Republicans Sanders campaign announces it contacted over 1 million Iowa voters Iowa Steak Fry to draw record crowds for Democrats MORE, seeking to highlight his ties to his former donor Antoin Rezko.

In its complaint to the Senate Ethics Committee, the group says that Obama violated the Senate's gift ban by buying a house from the Rezko's wife. The group alleges that Obama's purchase of another strip of land from Rita Rezko constituted a gift. Obama has said that real estate purchase was "a mistake."

Antoin Rezko has been convicted on fraud and bribery charges. Obama has not been linked to Rezko's case.

Read the ACU's full complaint here.