THE 32 U.S. senators up for reelection next year raised $20.6 million in campaign funds in the first six months of 1987. The money, a third of it from PACs, poured in at the rate of more than $110,000 a day. All told, the 32 have now raised $40.8 million since their terms began in January 1983. These are daunting sums -- and they are meant to be. You challenge these incumbents only at enormous cost. Opponents of campaign finance reform -- the bill now pending in the Senate to put limits to this mad cycle of raise and spend -- argue that the present system of no fetters works to the advantage of challengers; it lets them spend the extra that they need to win. It serves at least as much to perpetuate those already in power. It is in any case obscene, a threat to the integrity of the democratic process in whose name the shamelessness is carried on.

The dominant figure in the fund-raising is Lloyd Bentsen of Texas, chairman of the Finance Committee. He raised $3.8 million in the first six months of this year, a third from PACs. The senator, whose large state breeds expensive campaigns, has now raised $5.1 million since his term began, an eighth of what has been collected by the entire class combined. If these sums attest to his considerable virtues as a legislator, they are also a form of tribute to his powerful position.

In February it was disclosed that Mr. Bentsen, on becoming chairman of Finance, had set up a "chairman's council" made up of about 200 lobbyists and other operatives, who were invited to contribute $10,000 to his campaign and in return have breakfast with him once a month over the next two years. He would be relying on them not just for money but also for "advice," his letter of solicitation said. We were among the many offended by, if nothing else, the explicitness of the proposed arrangement. An embarrassed Mr. Bentsen disbanded the breakfast club and returned some $90,000 in contributions. Now it turns out that more than half the money has been given right back to the senator's campaign fund.

Does it make any difference how the money is given? Is the second way, to which we have all become accustomed, really any different from the first, which produced such indignation? Yes, in a sense. The proprieties do matter; they constrain. The breakfast club, with its implied offer of coziness for cash, strayed across the line. But no, in another sense; there is no difference. Sen. Bentsen does no wrong in accepting the campaign contributions; they are part of the system. But the system is rotten. The raising of campaign funds twists the Senate in a way that no one can regard as healthy.

The pending bill would cure the excess by imposing spending limits. The Supreme Court has said that spending limits standing alone violate the First Amendment, but as a condition for receipt of public funds they do not. The bill thus offers public financing of campaigns, but much reduced to satisfy Republican objections. The Republicans, in recent years better fund-raisers than the Democrats, have nevertheless filibustered; the bill has been stalled. Majority Leader Robert Byrd says stubbornly that he will try again when Congress reconvenes in September. He should. The Republicans are in the wrong position on this issue; it's time to dea