The president of the United States in RE4 was a man named Graham, the same last name as Ashley. It's common practice in all but a few instances of media to cast fictional characters in actual US politicians' places. The only exceptions I know of were the television series JAG which had actor David James Elliot digitally inserted into a scene with former president Bill Clinton and Transformers which had a George Bush impersonator cast for a brief scene aboard Air Force One.