If nothing concentrates the mind like the prospect of one's hanging, then Vice President Dan Quayle is doing some mighty clarifying. With evident glee and -- to my mind -- persuasive logic, Quayle has dangled the noose of term limitations before Washington. If the vice president had his way, a member of Congress would go home after 12 years -- an idea that, if it does nothing else, would rid the town of Jesse Helms. There is a splendid pearl in Quayle's oyster.

But the proposal appeals in other ways as well. "Americans are being denied competition in the electoral process," Quayle said the other day. The figures, of course, back him up. In the recent congressional elections, 96 percent of incumbents in the House of Representatives won reelection. In the Senate, only the hapless Rudy Boschwitz (R-Minn.) lost -- and this in a year when a sinister anti-incumbent mood had supposedly seized the American voter.

You might think that any idea endorsed by Quayle should be opposed by reasonable men. Alas, that is not the case when it comes to term limitation. For sure, the idea plays into the hands of the Republican Party, which, quite rightly, finds itself in a seemingly permanent minority in the House. It would take either term limitations or a killer flu for the GOP to once again take control of Congress -- and even then nothing is certain.

But what commends a term limitation is its Draconian quality: 12 years, and you're gone. Like the above-mentioned hanging, that ought to get the attention of the lawmakers in this town who will do almost anything to win reelection. We have at the moment the smarmy spectacle of the Senate Ethics Committee's hearings into the purported trading of influence by the so-called Keating Five. Keating, of course, is Charles Keating, whose defunct Lincoln Savings and Loan will cost you and me some $2 billion to bail out. The Five are senators, all recipients of huge donations from Keating to either their reelection campaigns or favorite causes.

What's instructive about this scandal is that none of the five appears to be an out-and-out crook. No money went into their pockets. One of them, John Glenn (D-Ohio), is as close as you can come to a genuine American hero: Korean War fighter pilot and first American to orbit the Earth. He's not in the Senate to become either famous or rich. Yet now the faint aroma of corruption clings to him -- all because he might have crossed an ethical line in the all-but ceaseless search for campaign funds. That line distinguishes the Keating Five from the Non-Keating 95 -- not any disdain for fund-raising. Ask a senator what he does more than anything else, and he'll tell you (if he's honest) that he raises funds.

The system stinks. The cost of campaigns is daunting to non-incumbents and corrupting to officeholders. Keating got an audience, because Keating's got the bucks. Either because Congress will not junk the present system or because it will not deal severely with the cost of campaigns (especially television ads), it has created a situation where you almost have to be born in Congress to get there -- and then, as in the House of Lords, you're there for life.

The American political system seems to be gridlocked. Incumbents win reelection because they can raise campaign funds. They raise their funds mostly from special interests. The special interests give only to incumbents. If the voter feels left out of this closed circle, he's entitled. If he wants to do something about it by limiting terms, he's also entitled. In fact, he's the boss. Look it up.

Term limitation has its problems. It is contemptuous of experience, from which, in theory, comes wisdom. It may compel lawmakers to rely excessively on their staffs and would, biannually, people Congress with a bunch of innocents who might swoon for the blandishment of lobbyists. And term limitation will mean that every member whose time has come will become unaccountable to his constituents. You can't vote against someone who cannot run.

But if the term-limitation proposal has a single virtue it's as a mighty roar of protest from the American people. In California and Colorado, voters last month approved term limitations for their legislators, and Oklahoma earlier this year passed a similar measure. With all due respect, Colorado and Oklahoma are one thing, California another. It was the golden voters of the Golden State who not only gave us Ronald Reagan but even earlier warned that a tax rebellion was brewing. Congress would be wise to pay heed. The voters are giving it a choice: reform the system, or get out of town.