Presidential illnesses often cause fear through the land for many reasons, not the least is that the vice president is one heartbeat away.

For the historical record, there have been very few popular vice presidents in history. Many of them have chafed under the shadow of their second-place roles, especially if they have coveted being No. 1.Furthermore, presidents rarely pick their running mates on the basis of whether they are confident that they, too, can run the country.

The reasons are much more selfish, mainly what constituencies and how many votes can the person bring in to help the ticket.

Another aspect is that most presidents have no reason to believe they will not be able to serve out their full terms. Often, they will pick relatively unknown men.

The fact is that a future president has the sole prerogative of picking his successor if a national tragedy occurs. Eight presidents have been assassinated or died from illness while in office.

John F. Kennedy, who was assassinated in November 1963, was the exception in choosing a fellow Democrat he knew could fill his shoes if he could not serve out his full term - Lyndon Johnson. Up to that time, there never was any question that Johnson's public career and political skills had prepared him for a larger role.

In addition to Johnson, in recent times two other vice presidents have become president: Harry Truman when Franklin Roosevelt died April 12, 1945, and Gerald R. Ford, who took the reins when Richard M. Nixon was forced to resign as a result of the Watergate scandal.

Each of the vice presidents tried to rise to the occasion and to put his own stamp on history. Johnson plunged ahead to create the Great Society social programs, but his downfall was the Vietnam War. Truman, a relative unknown except for outstanding work in the Senate, grabbed the ball and ran with it as president, arousing public admiration for his feistiness and courage. From the outset of his presidency, Ford decided that no new programs were in order and failed to personify his own stamp on the presidency. But it was the Nixon pardon that angered voters enough to defeat him.

President Bush's selection of Sen. Dan Quayle, R-Ind., a conservative, came as a stunning surprise to supporters who did not even know he was in the running, much less at the top of the Bush's list.

But Bush has repeatedly defended his choice, and a couple of months after he took office, the president said he would again tap Quayle as his running mate.

Starting out with two strikes against him and a heavy load of negative publicity, Quayle has borne up and is doing what all vice presidents are supposed to do: Carry the message to the people from the White House; raise money for the party, attend functions to elect party members and travel the world on goodwill missions. He also is recruited to attend state funerals.

Under the circumstances, it is pretty hard to shine, although vice presidents are put in charge of some programs that are important to the administration they serve.