THE BALLOON has gone up on congressional campaign finance. Senate Majority Leader Robert Byrd, facing a Republican filibuster that he lacks the 60 votes to break, has nonetheless called up the public financing bill of which he is cosponsor. The idea is to force a search for a compromise. The Republicans don't like the Democratic bill, but no one wants to be seen in the public embrace of the present system either. The reason is that the system is, if not corrupt, then fetid and at least embarrassing. That's also the reason for the Democratic bill. Mr. Byrd thinks maybe shame will help him move it. We hope so.

The Republicans, to guard against the charge that they are naysayers awash in cash, have come up with alternatives. The more responsible, because more straightforward, was by Sen. Ted Stevens in the Rules Committee. The PACS are where the strongest smells now come from. As the cost of campaigning has leapfrogged in recent years -- the average Senate seat now costs $3 million, a contested seat much more -- the PACs have become bankers. They gave $132 million in the last election cycle. The Realtors alone gave $2.7 million. The list of the 50 biggest contributors also includes such disinterested parties as the doctors, teachers, auto workers, Teamsters, home builders, trial lawyers, Seafarers, life underwriters, auto dealers, dairy co-ops, airline pilots, railway workers and rural letter carriers. All they want, of course, any of them, is good government.

Mr. Stevens suggested that PACs be permitted to give less per candidate than now, individuals and the parties more. That sounded virtuous; in many ways it is. It happens that Republicans are also better at raising individual and party money, but that's the Democrats' problem. Now a second alternative has been put forward by Sen. Bob Packwood and others. It is flashier; it purports to bar direct PAC contributions to candidates. But it would still permit them through the back doors of the parties, and critics say it would also legitimize the practice of bundling, whereby PACs evade the law by presenting large sums as the separate contributions of many individuals.

Too cynical, and in any case both these alternatives miss the point. The cost of office has doubled in the past 10 years; it is being bid out of sight. Expenditures are rising at a rate of some 20 percent per cycle. The Capitol floats on money; the members are obsessed with it. They will tell you so. It has to stop. There have to be limits. The Supreme Court has said there can be limits only in the context of public financing, as a quid pro quo for public funds. This is the sticking point for the Republicans. They argue against public funding as a form of piggery, Congress itself at the trough. That's doubly good politics for a party that both preaches smaller government and looks to its fund-raising advantage as the only way out of minority status. But public financing will not benefit just Democrats. It will cut different ways in different races.

The system now is wrong. The combination of spending limits in the context of public financing is the only way to right it. As both parties reach for compromise, there will be a temptation to rubberize the definition of reform. But there have to be spending limits. Otherwise they're just playing Fool the Vote