THE AVERAGE Senate reelection campaign now costs $3 million. To amass that much, a senator must raise $10,000 a week 52 weeks a year every year of his term. Let him miss a week for some reason -- could it be the press of legislative business? -- and he must raise twice that much the next week, three times as much the week after that. If he represents a large state or fears a strong opponent -- or wants to scare such an opponent off -- he must also raise more than average. And they do.

The system has become obscene. Its defenders argue that the money now in politics is a sign of vigor, a healthy form of participation. Yes, up to a point -- but that healthy point is past. The ceaseless quest for money absorbs the entire Congress, not only in election years. The National Journal recently compiled the amounts that senators not due to run until 1988 or 1990 had raised in 1985-86. By the end of last year four of the senators likely to run in 1990 had already raised more than $1 million; one was only $15,000 away; two more had raised more than $700,000. What notion of good government is served by that?

The Democrats seek to restore a sense of proportion to this process. They would impose spending limits. The Supreme Court has said that to satisfy the First Amendment, spending limits must be voluntary; as a practical matter that means they must be in return for federal funds. But Republicans object to public financing of congressional campaigns. The Democrats have therefore moved successively to minimize the role of public funds. Their latest proposal is that a candidate could get such financing only if he agreed to abide by the spending limits for his state and his opponent did not. The public money would be only an insurance policy.

It was easy for Republicans to block the Democratic bill when it contained a large measure of public finance; they could stand on principle. Now the issue is much more clearly the limits. Hard-liners still resist the bill, on grounds that the Republicans, who are better fund-raisers, would be condemning themselves to permanent minority status. But money isn't what will deliver the Senate to the Republicans; nor, in the long haul, can it be healthy for the Republicans to link themselves to this iron lung.

Two Republicans -- Robert Stafford and John Chafee -- have joined the Democrats in voting to invoke cloture and move a bill. At least half a dozen others have acknowledged the need for restraint. "There is no doubt that campaign spending is out of hand," said Sen. Pete Domenici at one point in last month's debate. "I would be very happy to see some kind of overall limitation," said Sen. William Roth. "I believe there is no surer way to a complete breakdown of our electoral process than to ignore burgeoning campaign costs," said Sen. Daniel Evans. "It seems to me there have to be some limits," said Minority Leader Bob Dole.

The latest bill is fair; the Republicans should agree to bargain on it. The alternative will soon be to change the name on the place. It fast becomes the U.$. $enat