The Jim Wright case gives the impression that corruption in America is on the rise. On the contrary. When it takes the speaker of the House 69 alleged ethics violations to garner $158,700, we can be sure that corruption in America is in decline.

For your average Middle-Eastern arms broker, this is an afternoon's work. For Michael Milken, a tip.Corruption on this scale I find sad.

Yet I am heartened by a certain island of integrity amid the pathos of this small-time sleaziness.

I cannot help feeling a sneaking admiration for the Texas Democrats who are fiercely sticking by their man, refusing to abandon a ship that is sinking.

Integrity is probably the wrong word to describe their motive. Loyalty is more like it.

But given what the House Ethics Committee reports is the state of virtue on Capitol Hill, we should be grateful for whatever shows of character we can find.

I am less impressed by the content of the Texas Democrats' defense of Wright.

The basis of the defense that Reps. Martin Frost and Charles Wilson and others are fashioning is that newly invented rules are being retroactively, and thus unfairly, applied.

Given the mountain of evidence presented by the Ethics Committee's special outside counsel, this is probably the best defense that Wright has.

It will carry no weight in the court of public opinion: People do not care when rules are created so long as they seem just.

But Wright's defense is designed to carry weight among members of Congress, who ultimately will decide his fate.

The point of the "retroactive rules" argument is this: If these are now the standards by which speakers are brought down, who among you is going to survive?

Indeed, congressmen were calling their Washington lawyers last week asking what to do about Wright-like skeletons in their closets.

How many congressional wives have Wright-like jobs where four years of work yields zero work product?

And how many congressmen can withstand scrutiny of the junkets, golfing weekends and other free lunches that they have enjoyed from friends who, like George Mallick, have a "direct interest in legislation."

Of course there is nothing at all retroactive about the rules. The rules on limits on outside income and on gifts from persons "with a direct interest in legislation" were established in 1977. What is new is that the standards are actually being applied.

Congress, which delights in investigating, exposing and ruining members of the executive branch, has conveniently exempted itself from similar scrutiny.

The crucial error, from the point of view of Congress, was permitting an outside counsel to poke his nose into the tent. Outside counsel brought outside values, i.e., ordinary American values and, using that novel standard, was shocked by what he discovered.

The 69 breaches of House rules that Richard Phelan found, and in which the Ethics Committee has preliminarily concurred, tell something about ethics on Capitol Hill.

More telling are the 47 violations which struck the outsider Phelan as appalling and the insider congressmen as acceptable.

Among these: Phelan found that Wright had spread rumors about the homosexuality of a federal bank regulator who refused to give a break to bankrupt Texas bankers, and demanded the firing of another who had unflattering things to say about Wright in the press.

Phelan cited these as ethical violations. He was overruled by the committee.

Only last month, Congress invented and retroactively applied new drinking rules for John Tower. Congress is now claiming retroactivity as a defense.

I enjoy a good irony, but I am far from cheered by the Wright debacle. The best that can come out of it is that Congress, now facing its own disgrace for a change, will next time hesitate before it allows a John Tower - like Jim Wright, flawed but talented - to be run out of town.

This might be the event that persuades Congress to abandon its post-Watergate pose as high-minded enforcer of petty virtue.

Petty, because the real corruption in Washington is the everyday, inherently corrupting dependence of congressmen on the lobbyists and the political-action committees who quite legally and, according to the book, ethically finance their campaigns and thus secure their futures. Beside the real scandal of campaign financing, Wright's nickel-and-dime pocket lining is a sideshow.

Or, from a slightly wider perspective, a sideshow of a sideshow. Historians of the next century will talk of the late 1980s as a time when the Soviet Union underwent a revolution, when East Asia first emerged as a world power, when Latin America took a great turn toward democracy.

They will have a sentence or two on the United States: "In Utah, a chemist claimed to have achieved nuclear fusion in a test tube.

And in Washington, Congress produced prodigious research regarding the drinking habits of a former senator and engaged in a mighty debate as to whether the speaker of the House sold books by the pound to the Fertilizer Institute."