GO:0001106

Interacting selectively and non-covalently with an RNA polymerase II repressing transcription factor and also with the RNA polymerase II basal transcription machinery in order to stop, prevent, or reduce the frequency, rate or extent of transcription. Cofactors generally do not bind DNA, but rather mediate protein-protein interactions between repressive transcription factors and the basal transcription machinery. [GOC:txnOH, PMID:10213677, PMID:16858867]