Searches for "Mr. Obama" bring up plenty of results, but more to the point it's a fairly common journalistic practice to use President Foo for the first mention and Mr. Foo for subsequent mentions. (Non-presidents usually get Mr. Foo and then just Foo.)
Here's an NPR story from the Obama administration about it: https://www.npr.org/sections/publiceditor/2011/10/12/1412934...