WHEN WALTER F. Mondale finally picks his running mate, one hopes this week, he will bring to a merciful close one of the saddest charades in recent political memory. Never before has a politician on the brink of such high office debased himself more before his supporters.

But all this is no surprise. The saccharine praise Mondale has heaped upon the token vice-presidential suitors visiting his Minnesota home and his public courting of the thoroughly over-rated New York Gov. Mario M. Cuomo are all a direct result of the candidate's excessive pandering to just about anyone or anything that would listen to him

He cajoled the National Organization for Women, the National Education Association, labor unions, dozens of governors, senators, and congressmen into endorsing him way before opening day in lowa, and now all his supporters are cashing in their chips at the same time. That is why Mondale has been forced to play this cat-and-mouse game with his backers, many of whom are now threatening to jump ship if they don't get what's owed to them.

Under normal circumstances, few of those paying house calls to Mondale would even have made the first cut. But tokenism carries the day, as completely untested local politicians are yanked out of obscurity and thrust into the national spotlight. Kentucky Gov. Martha Layne Collins gets consideration because of her great record in the state house God no, she only took office this year. She's being considered because she's the only Democratic woman governor in the country.

And what of W. Wilson Goode, the bright young Philadelphia mayor who resisted the heavy swing to Jackson in his city to back Mondale and even campaign for him. He hasn't been in office a year yet. And Rep. Geraldine Ferraro (D-New York). She's only a third-term congresswoman. Some pols have been languishing in the House and the Senate for decades waiting for chances like this.

Even Cuomo, who has become a party guru with his gospel of gee-whiz goodness, has no record to run on. His year and a half in Albany has been a litany of failure, and his obsession with the 21-year-old minimum drinking age as the family issue is too silly to warrant any serious discussion.

Mondale is in this jam because he has never been able to separate himself from the cliche his critics have created about him--the special interests mongerer. He was created as an embodiment of the party platform; everybody has a plank, and everybody gets what he wants. Mondale believes that he can win the election by adding up minority groups and pandering ad nauseam to women's groups. It won him a party nomination, but he earned it with only percent of the primary vote--compared to 36 percent for Sen. Gary W. Hart (D-Colo.)--which makes him an even weaker nominee than George S. McGovern was in '72, and we all know what happened to him.

MOST AMERICANS like to think of themselves as, well, Americans, not a walking, talking, cultural stereotype with an issue button that is just waiting to be pressed. One hopes that Mondale will just swallow hard and pick Hart, so that, the nominee isn't eaten alive by his supporters.

But after this sad spectacle, any popular, experienced contender will keep away. Gary Hart knows a sinking ship when his spiritual advisor tells him he sees one.