For the forty or so years that I have followed politics it has always been President XXX the first time in an article and then President mixed with Mr. This is to lower the repetitiveness of using just one and is done no matter who is the President.
I'll give them a pass on written articles, reluctantly, however what excuse is there when newscasters/pundits continuously do it? Listening to Juan Williams, Campbell Brown and many others, you'd think GWB was an average joe and not our President.