Jimmy And Barack

JIMMY AND BARACK....Ben Smith reports the following from Jimmy Carter:
Don't forget that Obama won in my state of Georgia. My town, which is home to 625 people, is for Obama, my children and their spouses are pro-Obama. My grandchildren are also pro-Obama. As a superdelegate, I would not disclose who I am rooting for but I leave you to make that guess.
Very cute. But I don't get it. Why, "as a superdelegate," would he not disclose who he favors in the primary?