Public discussion all over America quite naturally is centered on the health of George Bush, who suffered atrial fibrillation - or irregular heartbeat - while jogging near Camp David this past weekend. The president, blessed with vigor and good health, has been identified as a man with abnormal faith in the virtues of perpetual motion.

Americans of all political persuasions can be genuinely relieved that Bush's problem is not considered life-threatening and is responding to medication - and that the president has returned to his duties in the White House.While it is commendable to see the 66-year-old president so active and conscious of physical fitness, it should be remembered that actuarially he is past retirement age. That is not a liability by any means. It gives him a great well of experience to draw upon. Ronald Reagan was a two-term president in his 70s.

Nevertheless, health can be a concern, although the president clearly has access to the finest medical care the world can offer.

Yet the weekend hospitalization of Bush does raise another issue of genuine concern - succession to the presidency. Even though it was finally deemed unnecessary, it was originally announced that Bush would undergo an electric shock procedure to stabilize his heartbeat - meaning that Vice President Dan Quayle would temporarily assume the duties of the presidency.

Had Quayle done so, under the provisions of the 25th Amendment, he would have been doing what Bush as vice president did when then-President Reagan underwent colon cancer surgery for eight hours.

The mere brush with such an eventuality already has given rise to new speculation about the fitness of the vice president for the presidency. According to a recent poll of Americans conducted by CNN and Time Magazine, only 19 percent consider Quayle qualified to take Bush's place, while 66 percent think him unqualified. Even 58 percent of fellow Republicans do not consider him qualified.

Although Bush has always maintained that he would keep Quayle on the ticket in 1992, that stand has mostly been based on political considerations, not the president's health.

Even though any vice president should be the next most qualified person in the country to be president, presidential candidates tend to select running mates for more pragmatic reasons, such as geographic and political balance for the ticket.

As cynical as it sounds, some presidential candidates have purposely chosen running mates who were less well known and less likely to steal the limelight.

Although Quayle's image unquestionably has been battered by an unending flood of jokes about his capability, it may very well be that the critics are wrong. Other vice presidents, such as Harry Truman, who initially seemed unqualified, have risen to the occasion upon the death of the president.

Nevertheless, it is time for a second look. And if Bush knows enough about Quayle to be convinced that the critics are wrong, he should share that knowledge with the public.

It has been said before that Quayle is only one heart-beat away from being president. That statement takes on a new sense of somber reality and meaning since Bush's unexpected stay in the hospital.