The brave old Chief and the Kinderhook Squire

RONALD Reagan's skillful handling of the age issue in the second TV debate will enable him to add to his margin as the nation's most senior President when he is inaugurated next month. This was not, however, the sole instance of a chief executive's making political hay out of his relatively advanced age.

In the interest of historical accuracy, it should be noted that William Henry Harrison, the second-oldest candidate for the presidency, was the first to use his age - 67 years - to advantage, in the campaign of 1840. Opposing Democrats did everything possible to accentuate Harrison's ebbing years. They called the Whig candidate ''Old Granny'' and made fun of the fact that he had a hard time putting his thoughts together in his speeches.

What's more, Democrats ridiculed the fact that Harrison, a former Indian fighter at the Battle of Tippecanoe, was running for the nation's highest position after having held an appointment as a drowsy clerk of the Court of Common Pleas in Hamilton, Ohio. But Harrison and his followers used the strategy of an ''old soldier and farmer'' running for office. They created the image of a log cabin settler who still had the capacity to go after a ''parcel of long, slab-sided, lop ear'd hogs.''

And ''Old Tip,'' as Harrison was dubbed, gave not a little emphasis to the fact that he did things differently, even awkwardly. ''I am not a professional speaker, nor a studied orator,'' he said, ''but I am an old soldier and a farmer , and as my sole object is to speak what I think, you will excuse me if I do it in my own way.''

The crowds ate up such talk, as they did Harrison's appearance. One contemporary described him as ''about 5 feet 9 inches . . . very slender and thin in flesh, with a noble and benign expression of countenance - a penetrating eye, expansive forehead and Roman nose. He is not bald but gray, and walks about very quick, and seems to be as active as a man of 45. . . .'' When Harrison was slow in addressing the crowds, that was fine, because such was ''becoming his years, his dignity of character.'' And when he couldn't think of anything to say , he didn't, which led his critics to call him ''General Mum,'' a term of endearment among supporters.

President Martin Van Buren, called the Kinderhook, N.Y., Squire by his foes, didn't have a chance in a campaign that witnessed an outpouring of support, even in songs, for Old Tip. One of the most popular ballads was ''The Brave Old Chief'':

The brave old Chief, who brought us relief,

In the time of our sorest need,

Exalt we his name, to the summit of fame,

For Glory's his well-earned need;

If people enquire, for the Kinderhook Squire,

And the fate of his Tory clan,

We'll reply they are dead, in their sour-krout laid,

To make room for a much better man.