George Bush has already been president of the United States. It says so in his campaign biography. The day was July 13, 1985, and for eight hours, while Ronald Reagan was undergoing intestinal surgery, Bush was acting president.

What the resume doesn't say is that during his eight hours at the top, Bush slipped during a tennis game, banged his head and was out of commission himself for part of the time Reagan was under anesthesia.

"Out of commission" is the only way to reconcile disputed accounts of this previously unreported incident. Our sources, including high-level White House officials, told Dale van Atta that Bush was reportedly "unconscious" for a time. But a top Bush press aide said he was never "incapacitated," though he did "sleep it {the injury} off."

Here is what happened:

July 12, 1985 -- Reagan was admitted to the Bethesda naval hospital for examination of a polyp in his intestine. Bush flew off for a vacation at his house in Kennebunkport, Maine. During the exam, a second growth was found and Reagan decided to have it removed the following day.

July 13, 9:30 a.m. -- Bush left Kennebunkport on Air Force Two, feeling he should be near the president while he had the job of acting president.

10:32 a.m. -- Reagan signed letters to then-House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) and then-Senate President Pro Tempore Strom Thurmond (R-S.C.). The letters said Bush would be in charge while Reagan was in surgery and under the anesthesia.

11:28 a.m. -- Reagan went under anesthesia and Bush became acting president. A top-secret exchange of nuclear codes and authority was made over secure communications to Bush aboard Air Force Two. His finger was on the button then.

Noon -- Bush arrived at Andrews Air Force Base and went to his residence at the Naval Observatory in Washington. He later told reporters he passed the day reading and talking on the telephone. Nothing presidential happened.

Nothing, that is, unless you're talking President Gerald R. Ford, the king of the pratfalls. Sometime during the afternoon, while Bush was playing tennis, "he slipped and hit his head, but was not incapacitated," a Bush aide told us. "It wasn't serious enough to be checked," he said. He simply "slept it off." Bush never mentioned the accident when he told the press how he spent his day.

7:22 p.m. -- Reagan woke up and, though still on painkillers, was asked if he was ready to reassume the powers from Bush. "Gimme a pen," Reagan exclaimed.

Bush's 7 hours, 54 minutes as acting president were over, but apparently not without incident.

Today, Bush's two-page campaign biography notes his role as "acting president," but it falsely states that this was "an historic transfer of authority from President Reagan under the 25th Amendment to the Constitution."

The only thing historic about the transfer of authority was the fact that both president and vice president may have been out of commission at the same time.