WHAT HAPPENED TO the new rules governing campaign financing? A lot of people thought the influence of big money had been curbed by those post-Watergate "reforms". Yet over $150 million, a record sum, was spent in this year's Senate and House campaigns. And conspicuous roles were played by wealthy candidates, ideological and single-issue groups, and swarms of political action commitees (PACs) - the kinds of monied forces that the new rules were meant to restrain.

In part, this shows how the 1974 campaign-finance law was confounded when it ran into the First Amendment. While upholding limits on donations by individuals and interest groups, the Supreme Court ruled in 1976 the the spending of one's own money could not constitutionally be restrained. That gave a huge edge of rich, free-spending candidates and those who attract large numbers of small contributions through ideological or single-issue mail appearls.

The "reform" laws also encouraged corporate PACs and, by providing public financing of presidential campaigns, channeled the special-interest money - a staggering $60 million or so - toward Capitol Hill. Most of this year's biggest spenders were familiar - medical groups, the dairymen, the maritime crowd, other unions, the trial lawyers and such. With over 700 corporate PACs reistered, though, other business giving is bound to grow. The picture could change drastically for the worse if the Supreme Court should somehow dicide one day that corporate money, now looming large in issue-oriented fights around the country, may no longer be barred from federal campaigns.

The big money did not always prevail yesterday - it never does. Nor does it always pull the same way. The PACs traditionally give about two-thirds of their largess to incumbents. Personal wealth and one-issue crusades are wild cards that may bolster an incumbent or propel an outsider into prominence, help a liberal or a conservative. Yet those forces have at least the capacity to be preemptive, especially against challengers without generous funding of some sort. And the rise of those elements further erodes the role of party coalitions, helping make campaigns and Congress more fragmented and volatile.

That's where partial reform has brought us. If you find the scene at all disquieting, as we do, the next question is whether the best remedy is more "reform" - or less. There are several possibilities to mull over while reading yesterday's returns.

The tireless "reformers" spurred by Common Cause want to press on toward public financing of congressional campaigns and other uses of law to curb or counterbalance private interests. Yet even if you believe a larger "public" - i.e., governmental - role in politics is desirable in principle, the obstacles are great. It's hard to believe that constitutional problems can be overcome; that all the grey areas of political practices can be clarified, codified and even-handedly controlled; that the Federal Election Commission can be freed from the grip of congressional leaders, and that Congress, an assmeby of incumbents, will agree to give challengers a better break.

A more modest "reform" approach might try to promote more healthy competition within the current system of private finance. This could involve easing the constraints on political parties, trying to bring down the cost of campaigns, and giving congressional challengers aids such as lower mailing rates.

The third possibility is to deregulate - to maintain the disclosure laws, but lift controls on political giving and leave judgments on excesses mainly to the voters at the polls. This, too, involves large risks, especially with campaign costs so high and voter participation often so low. Some congressmen would no doubt continue to be bought or rented by various interests; some candidates would no doubt be swamped by lavishly financed campaigns. Yet this course does accord more with the First Amendment. It acknowledges that open competition among interests, "special" and "public," is a staple of democracy. It vests more faith in the public - and grants less automatic influence to money - than courses that assume too much free enterprise will stifle politics.

The basic question, then, is which kinds of defects and political distortions one regards as most harmful and dangerous. That is surely worth thinking about before launching a new crusade to "purify" campaigns.