For many years (and multiple presidents), ABC7 has referenced the President of the United States as "President" in the first reference, and "Mr." in subsequent references.
In fact, the President is the only person ABC7 gives the "Mr." honorific to on second reference. AP style actually only requires "Obama" on second reference.
Mr. Obama is not the first president to be referenced this way on ABC7. Here's an example of ABC7 calling President George W. Bush "Mr. Bush" on 2nd reference.