Union Home Minister Rajnath Singh on Sunday said the Congress, rejected by the people of Tamil Nadu several decades back, is trying to return through the back door.Addressing a poll rally for poll ally AIADMK's candidate N.R. Sivapathy for the Perambalur Lok Sabha seat, he said that the Congress is trying to get a foothold in Tamil Nadu through an "opportunistic alliance" with DMK.Rajnath Singh also said that many people in both the DMK and the Congress are on bail.