Hm, not sure, but I think Brian Williams might be wrong.

http://www.infoplease.com/ipa/A0001618.html

No, I think Brian Williams is right, not matter what one Marian-Grammarian website says.

George H.W. Bush is consistently addressed as "Mr. President," or "President Bush." Same goes for Senators, Congressmen, Governors, etc.

As an example, when Christine Todd Whitman was EPA Administrator, she wasn't addressed as "Administrator Whitman" (in the way that Carol Browner was addressed as "Administrator Browner) but was addressed as "Governor Whitman" - even in EPA publications.