If you’ve won an election fair and square, there should be no need for your opponent to formally concede. (Regarding “Update II”, for which scroll down.)
All that really needs to happen is for the election commision to certify the vote and the Capitol Police to change the locks on former Congressman Maffei’s office door. You lose. Get out.
A "surly curmudgeon[], suspicious and lacking in altruism." (Robert A. Heinlein)