How many acting presidents have there been?

Answer 1

To date (2012) there have been two Acting U. S. Presidents:

• George H. W. Bush (12 July 1985)
• Dick Cheney (29 June 2002 and 21 July 2007)

Some argued that John Tyler, who was Vice President the first time a U. S. President died in office, became Acting President, but Tyler proclaimed himself to be every bit the U. S. President as his predecessors had been. Nobody legally challenged his assertion, and his precedent was followed by the seven other Vice Presidents who found themselves in his situation until it was finally put in writing about 125 years later in the 25th Amendment to the U. S. Constitution.