THEY'RE AT IT again. The usual group of well-intentioned Good Government Advocates has now created a blue-ribbon panel, led by such luminaries as Milton Eisenhower and Lloyd Cutler, to push for a single, six-year term for the presidency. If only we could remove the shackles of unseemly politics from our presidents, they argue, a wonderful world of better policies would follow.

Besides being elitist and undemocratic, they are wrong. It is politics, and the threat of reelection that a president can wield, more than anything else, that keeps a president from being rendered impotent. It is also the prospect of reelection that keeps our political dialogue, for at least a short while, focused on the current occupant of the White House and not on his likely successors.

A single six-year term would create both a six-year lame duck and a 51/2- year presidential election campaign -- both prospects too horrifying to imagine. Indeed, if we wish to come up with a constitutional solution to the problem of presidential impotence, we need to go in precisely the opposite direction -- and repeal the 22nd amendment to the Constitution that limits presidents to two terms of service.

The 22nd Amendment was initiated, drafted and passed by the first Republican Congress after Franklin Roosevelt, clearly as a reaction to his unprecedented four-term success. The amendment was ratified on Feb. 27, 1951 -- much to the regret of many GOPers soon thereafter, when they elected their own Roosevelt, Dwight Eisenhower. In spite of their protestations to the contrary, Republicans pushed through the 22nd Amendment for political purposes, not with any great theoretical purpose behind it.

Enacted for political purposes, then institutionalized into our political culture, the amendment clearly was a mistake. By creating an instant lame duck for the second and last term of a president, the amendment made second presidential terms less palatable and less powerful, for presidents and for electorates.

By limiting any president to a maximum of eight years in the White House, far less than the tenure of the average powerful committee chairman on Capitol Hill, the amendment created a greater spirit of intransigence in Congress; every chairman knows that he is likely to be around (as are the affected lobbyists) long after the president has departed, giving him more incentive to delay, defy or deflect presidential directives or requests.

Presidents have power -- much of it political power. Every president, no matter how weak in the polls, is a strong possibility for reelection, given the weapons of the Oval Office, That power, and the attendant possibility that the president will be around to deal with for a much longer period of time, give recalcitrant congressmen pause, and give the president more clout.

In addition, the ever-present possibility that a president will seek reelection gives pause to potential rivals within his own party. As long as Ronald Reagan considers running again in 1984, the activities of such prospects as Bob Dole, George Bush, Howard Baker and Jack Kemp are focused more on the policy process and less on campaign organization. Moreover, their motives are less suspect to colleagues and press, enabling them often to do more in policy.

Imagine the speculation that would have surrounded Dole's effort to enact a tax bill in 1982 if the GOP nomination for 1984 had already been declared open; positions of many senators and House members might have changed if presidential politics had been added to the equation, and the tax bill might well have failed.

Moreover, every action inside the White House, from George Bush's schedule to Jim Baker's press interviews, would be totally interpreted in terms of the coming horse race. All this nonstop gossip and speculation would cripple Ronald Reagan,in not help him or his program.

It is no surprise, then, that every signal sent by the president about his 1984 intentions is positive, including the appointment of his best friend Paul Laxalt as top dog at the Republican National Committee. The longer Washington politicians think they might have Ronald Reagan to kick them around some more, the more respect they will have for his efforts at persuasion. If he decides not to run in 1984, we can expect little if any of his substantive program to be enacted thereafter.

Even if Reagan runs and wins in 1984, he will be a lame duck for the succeeding four years, leading to the same loss of power, backbiting and wholesale speculation about his successor described above. We can do much for the presidency, the system, public policy and democracy, by repealing the president-shackling 22nd Amendment, and returning to the election system our Founding fathers intended.