Some Democrats have already found their candidate for 1988. It's Mario Cuomo, the governor of New York, who disclaims any presidential ambition. They see in Cuomo all the strength, brains and intellectual machismo they could ask in a standard bearer.

He is, they argue, an unmistakable, unblushing Democrat, a liberal who is committed to family values and an orator without rival in the party and possibly in the country. Unlike most other Democrats, he is perfectly willing to do battle with Ronald Reagan.

Cuomo came to Washington for a day this week and displayed his virtues and shortcomings.

He made a speech to a packed audience at the National Press Club on Reagan's tax reform bill. He was commanding -- and entertaining. His impersonations of various taxpayers reacting to details of what would really happen to them in the Reagan program produced great hilarity.

He expressed fervent federalism -- he thinks of the states as members of a large family -- in vivid, forceful terms. He replied to an administration comment that "the sharks are getting ready to bite" on the president's package in this wise:

"It's true that the sharks are gathering. But that's because there's blood in the water. Our blood.

"The blood of the states and localities being told that there's no room in the federal lifeboat. That if some are to prosper, the rest of us will have to be thrown overboard."

We are all in it together, he asserted, striking a favorite theme. It is not a question of 35 low-income states "subsidizing" 15 high income states, such as New York, as the president is wont to say:

"Just follow that the logic of that assertion for a moment. Is it right that the residents of New Jersey spend their money to subsidize farmers in Iowa? Why do Iowans contribute to mass transit in New Jersey? Why do the people of Alabama help build dams in the northwest? "

His answer to his own questions: "Of course it is. In our federal system we're all stronger when each part of the republic is able to meet its needs."

Many congressional Democrats are delighted at his powerful intervention on an issue that left them, they thought, no choice but to go along. They fear opposing Reagan on a pet project. They shrink from being labelled "negative" or "obstructionist."

Pleased as they are that he will take on Reagan, they are dismayed that he is having a brawl with Reagan's communications director, Patrick Buchanan, who in typically lurid expression called Cuomo a "glib, fast-talking lobbyist for a reactionary liberalism," a "neo-socialist," guilty of "unbuttoned bellicosity," "nastiness" and "falsification."

The governor responded that Buchanan's remarks were "a stunningly irresponsible castigation of all states struggling to meet their needs."

Rep. Tony Coelho (D-Calif.), chairman of the Democratic Congressional Campaign Committee, said that "A governor doesn't get into a spitting contest with a White House staff man."

The Republicans are delighted that Cuomo rose to the Buchanan bait and is so embroiled with a pugnacious subordinate instead of the president himself.

"We never thought he would bite," said one of them. "This diminishes him."

But Cuomo insists that the exchange of unpleasantries has helped focus public attention on his crusade for fairness in the tax bill.

Still, Democrats think it may be a sign that in a national campaign a Republican rival would find it comparatively easy to get Cuomo's goat.

And he showed that he is capable of going over the side in vituperation. At the roast of him held Wednesday night at the Washington Hilton, he called Buchanan "one of a kind -- unless you count Khaddafi."

One of the roasters, Democratic National Committee Chairman Paul G. Kirk Jr., pointed to a graver vulnerabili, the governor's blank record on foreign policy.

"I heard Cuomo talking about tax reform in New Jersey," said Kirk, "and when someone asked him how the president's program would effect a family of four in Perth Amboy, the governor said, 'I never take foreign policy questions.'"

Actually, it is in foreign policy that the bedraggled Democrats are most split and sorely tried. It isn't the economy, or race, that divides them now.

It is on cosmic questions like the MX, where Democratic collaborators helped Reagan keep the missile alive, or aid to the Nicaraguan contras -- where they finally gave way -- that the surrenders are occurring. Hours before the roast, the Democrats, who have held out for three years against Reagan's chemical warfare buildup, capitulated again.

Cuomo will take on Reagan. But is he willing to take on Democrats who think their salvation lies in blurring the differences between themselves and the Republicans? Cuomo may rather remain governor of New York than become the leader of a party that can't decide whether suicide or extinction is preferable.

Mary McGrory is a Washington Post columnist. effect a family of four in Perth Amboy, the governor said, 'I never take foreign policy questions.'"

Actually, it is in foreign policy that the bedraggled Democrats are most split and sorely tried. It isn't the economy, or race, that divides them now.

It is on cosmic questions like the MX, where Democratic collaborators helped Reagan keep the missile alive, or aid to the Nicaraguan contras -- where they finally gave way -- that the surrenders are occurring. Hours before the roast, the Democrats, who have held out for three years against Reagan's chemical warfare buildup, capitulated again.

Cuomo will take on Reagan. But is he willing to take on Democrats who think their salvation lies in blurring the differences between themselves and the Republicans? Cuomo may rather remain governor of New York than become the leader of a party that can't decide whether suicide or extinction is preferable.