Alan Cranston, California's senior senator and the assistant Democratic leader, has the somewhat cadaverous look characteristic of today's hyper-healthy joggers. He is 67 and exercises like mad, even competing in sprints at track meets restricted to people old enough to know better.

>And now he is making the preliminary noises and maneuvers that are expected from people in the early throes of running for president. A friendly committee has been organized to be a wetted finger in the Breeze of History and to be, simultaneously, a dry finger on the Pulse of the Republic. In due time it will report that in Alan Cranston, the man and the moment have met.

Well, why not? It's a free country. And in 1980 in California, where one- tenth of America's electorate lives, his victory margin was about 1.5 million. He ran 200,000 votes ahead of Ronald Reagan's pace, carrying 52 out of California's 58 counties. He is the first California Democrat to win a third Senate term.

Cranston is a liberal's liberal, so the first question is: Aren't Ted Kennedy and Walter Mondale enough, already? But perhaps (or so someone in Cranston's position must hope) Kennedy won't run. Perhaps Mondale will be as tedious a candidate in 1984 as he was in his short-lived presidential campaign before 1976. And perhaps Cranston can find an issue.

Cranston insists (as liberals are inclined to do these days) that he is a liberal-with-a-difference. His difference, he says, is that he has supported business tax cuts. But such support is no longer novel, even among liberals.

What would be novel would be for liberals to square their support for business tax cuts with their professed abhorrence of "trickle-down" policies. Businesses do not pay taxes, they collect them. They must pass taxes on as operating expenses. And tax cuts "trickle down" (if you will pardon the expression) to employees, shareholders, consumers and persons who get new jobs created by business expansion.

If Cranston's candidacy ripens, it may be most interesting as an instrument by which a latent issue comes alive. The issue is the independence of the Federal Reserve Board. The fascinating fact is not that Cranston seems inclined to seize this issue, but rather that it has gone so long unseized in an era of high interest rates.

Cranston, like some conservative monetarists, paraphrases what Clemenceau said about war being too serious to be left to generals. Cranston thinks that the money supply is too important to be left to central bankers. He has not decided precisely what should be done, but would consider: making the term of the chairman of the Fed coterminous with that of the president; or making the terms of all board members coterminous; or making the entire board serve at the pleasure of the president, and putting the board in the executive branch, in the Treasury, under presidential control.

There are two related arguments for this. One is that an independent Fed is an anomaly in a democratic system, because all who exercise power should be held directly accountable to the electorate. But this argument reads too much rigor into democratic theory, and ignores the American practice of tempering democracy.

The second argument is that because the president is held accountable for the performance of the economy, he should have powers commensurate with the public's expectations. He is expected to formulate fiscal policy, and so should be able to synchronize monetary policy.

There is, indeed, a radical asymmetry between the large economic duties assigned to the president by public opinion, and the weak executive instruments for performing these duties. But the primary incongruity is the institutional feebleness of the president's control of the budget. That could be addressed by giving the president a line- item veto--the power to veto particular items in appropriations bills.

Still, if Cranston articulates discontents about the Fed, he will frame the argument and challenge others to argue this more sensible position.

Americans tend to believe that clever institutional arrangements can compensate for the absence of particular social values and virtues. But no institutional tinkering--not with the veto power, and even less with the Fed--can fix what is broken. What is broken is the budget process. And that is a symptom of the weakness of those political and cultural values, such as public-spiritedness, discipline and farsightedness, that a serious budget process presupposes.

Cranston is not apt to be the Democrats' nominee. But he may start an interesting argument. If so, he will contribute more to the public good than many candidates do.