Dan Quayle’s endorsement of Republican Mitt Romney in Arizona on Tuesday brings to mind Quayle’s tenure as vice president for President George H.W. Bush back in the early 1990s, and the time he almost assumed the powers of the presidency.

Here’s what happened.

Bush suffered a rapid heartbeat while jogging at Camp David on May 4, 1991, and was rushed to Bethesda Naval Medical Center for treatment.

At the time, there were immediate fears that Bush had a heart attack. Communications among White House staff and the press corps were difficult in this pre-Blackberry era, and there was a lot of confusion.

At the hospital, Bush was diagnosed with atrial fibrillation related to a thyroid disease. Doctors thought they might have to give his heart an electric jolt to shock it back into a normal rhythm, which would have required Bush to go under anesthesia, making him incapacitated for a brief period. White House staffers drew up papers invoking the U.S. Constitution’s 25th amendment, which would transfer power to Quayle as acting president.

Americans were generally not thrilled with this prospect, since Quayle had once famously misspelled “potato” as “potatoe” for schoolchildren and had for the most part not distinguished himself in the job a heartbeat away from the presidency.