The Senate debate on campaign-finance legislation has been fascinating. Unlike the Persian Gulf, contra policy and the Strategic Defense Initiative, this is a subject on which all senators have become experts. They have to, because they spend so much of their time fund-raising.

What really fuels the current, and quite genuine, effort to change the laws is that most of the senators have come to despise their fund-raising chores. Those who retired from the Senate last year -- from liberal Tom Eagleton to conservative Barry Goldwater -- were blunt in condemning the obscenity of the constant search for dollars to meet the rapidly rising cost of the next campaign.

Freshmen elected last fall feel no less demeaned. Sen. Harry M. Reid (D-Nev.) said in debate that when he was contemplating trying to move from the House to the Senate, he went to a friend who had made the switch in 1984. ''The senator said, 'Harry, you are going to have to spend 70 or 80 percent of your time raising money if you want to be elected to the U.S. Senate.' I frankly did not think he was relating to Harry Reid. I am from the sovereign state of Nevada and we do things differently out there. . . . Sure enough, my friend was right.''

Sen. Brock Adams (D-Wash.), coming back to elective politics in 1986, 10 years after his last House race, was appalled by the changes: ''I never imagined how much of my personal time would be spent on fund raising. . . . When I was preparing to debate my opponent, my best opportunity to make my case on statewide television, I had to interrupt these preparations constantly to make fund-raising calls.

''I do not think a candidate for the U.S. Senate should have to sit in a motel room in Goldendale, Wash., at 6 in the morning and spend three hours on the phone talking to political-action committees . . . to the folks who make a living figuring out the odds on each race and betting on the percentages. I wish I had been able to win by debating the issues with my opponent rather than debating my political prospects with political banks.''

The experience Adams and Reid described is little different for incumbents, except that they now begin shaking down potential contributors three, four or five years in advance of election, stealing time from their jobs for the work.

What really gripes the senators is that they hand over 70 or 80 percent of the money they collect to the television-station owners in their states. Candidates have become ''bag men for the TV operators,'' as one senator put it in an interview. They also know that the rising tide of commercialized politics is turning off the voters.

Most of them would like to get off that merry-go-round, but because they are real-world experts in money-raising, not ivory-tower reformers, they can't help worrying about the practical consequences of some of the suggested remedies.

They know that while disclosure requirements have generally worked well, prohibitory regulations have not. Bar money from one channel and it tends to find its way to another.

They also know there are genuine costs and genuine risks in going to a system of public financing. It has worked quite well in the presidential campaigns since 1976, and the victories won by two of the first three challengers to incumbent presidents refute the Republican argument that public financing would be a virtual certificate of reelection for the Democratic majority in Congress.

But there is a cost to that system. Public financing in presidential campaigns has meant a virtual shutdown of local headquarters financed by small contributions. Grass-roots democracy has died.

And there's a political risk in dipping into the Treasury for campaign funds, even through a voluntary checkoff on the income-tax form. It did not escape any senator's notice that the only spontaneous applause from the tourists in the gallery came when Sen. Phil Gramm (R-Texas) called taxpayer financing of congressional campaigns ''a totally alien idea to American democracy.''

So what is to be done? There's a strong disposition on both sides of the aisle to limit contributions from interest-group political action committees (PACs). The Democrats propose to restrict candidates' dependence on them; several Republican senators would go further and abolish PACs entirely.

The other idea that is gathering support in the Senate is borrowed from a bill introduced by Rep. Al Swift (D-Wash.). The Supreme Court has ruled that absent public financing, Congress may not impose mandatory limits on campaign spending. Swift's proposal is to induce congressional candidates to accept voluntary limits by offering discounts on television time and postage only to those who accept the caps. Whether the 30 percent differential is enough of an incentive to induce candidates to accept an armistice in the spending race is uncertain. But it has caught several senators' imagination.

The technicalities are endless, but the public will be watching to see whether the Senate is too addicted to its self-destructive fund-raising methods to kick the habit. It's a test of whether the lawmakers can prevent a scandal -- or only react after one has occurred.

BY H. L. SCHWADRON