"They all do it." That's the knee-jerk defense whenever a politician gets into trouble in this town.

Every day for months, we heard it during Watergate. They all do it, Richard Nixon's fans said - What about Lyndon Johnson and his TV station? What about Bobby Baker? Apologists for errant politicians have been saying it at least since the First Congress convened in New York, two centuries ago this spring.When the first tariff on imports was about to be passed, something mysteriously held it up. Investigation showed that Rep. Thomas Fitzsimons of Philadelphia and others had a personal interest, in the form of ships then at sea. They were delaying passage until their cargoes were safely ashore. Fitzsimons' colleague noted for posterity that whenever a man acted as both merchant and congressman, "you will always find the merchant uppermost."

They don't all do it, but at any given time, somebody's doing it. The old saw is an effective reminder to either party that it had better not be too tough on the opposition this week, because next week the tables might be turned.

The cliche applies more accurately to the Jim Wright case now at hand. "They" don't all have their wives on a friendly developer's payroll, and they don't all work out book royalty deals as cozy as the one he had with a Texas friend. But "they," if we mean congresspeople, do indeed have such imaginative ways of supplementing their paltry $89,000 salaries that righteous taxpayers sizzle every time the subject arises.

Wright, when he went public to say he would fight allegations from the Ethics Committee, didn't quite utter the old defense on his own behalf. Plenty of other Democrats have done that for him.

He said "I am confident that in the 34 years I have served in the Congress I have not violated any of those basic rules or any commonly accepted standard of ethical conduct." That last phrase comes closest to "They all do it." It is a wise choice of words, because the commonly accepted standard of ethical conduct is remarkably tolerant - in Washington and around the world.

It used to be even more so. One of Wright's problems is that he has been here a long time, since he was merely 32. He grew up in old-style Texas politics. Helping constituents and being helped by them was the norm there and then. Here and now, standards have changed. Since Watergate, new rules have been written. Smart politicians stay within them.

Wright could have defended himself by citing Ed Meese and the battalion of other recent Republicans guilty of either the crime or the appearance of wrongdoing. That would be pertinent, but not admissible in his case. He is caught by rising standards, plus the determination of many Republicans to get even for Senate rejection of Tower as Defense secretary.

Much hypocrisy is involved, but the country is served by those rising standards. The objective citizen should be delighted to see the new political morality prevail in the case of the gentleman from Fort Worth, the Speaker of the House.

After that, let the same standards prevail in the whole Congress. They should be applied first to Wright's main tormentor.