John Sununu played his unique role last Friday afternoon by paying a discreet visit to Sen. Edward M. Kennedy and handing him anti-quota amendments to abort a Bush veto of the Kennedy-Hawkins civil rights bill.

The White House chief of staff was also taking a personal hand to restrain John Frohnmayer, the out-of-control chairman of the National Endowment for the Arts. His goal: ally the administration with, not against, Republican congressmen seeking common-sense restrictions on tax-paid art subsidies.

Sununu's double-barreled rescue operation is to save George Bush from seeming to favor racial quotas and federal funding of obscene art. This is not interfering with Bush-being-Bush, since the president clearly opposes both. It is Sununu's way of ensuring that his leader's zeal to be kinder and gentler does not lead him into political cul-de-sacs.

If Sununu doesn't do it, it won't be done. While he was in Costa Rica a month ago, other aides seemed to be putting Bush on record for the Kennedy-Hawkins bill, which Justice Department lawyers say mandates quotas. The civil rights community was getting the message: no way will this Republican president, proud of 50 percent approval from black voters, veto a bill with a civil rights label.

That was the signal from a private meeting between presidential assistant James Cicconi and ex-transportation secretary William Coleman, a prominent black Republican. It was reinforced to civil rights leaders by Bobbie Kilberg, a liberal Republican who heads public liaison at the White House. Press Secretary Marlin Fitzwater confirmed the supposed switch by proclaiming only ''minimal'' differences between the president and the bill sponsored by Kennedy and Rep. Augustus Hawkins (D-Calif.).

The walk back from that leap began a few days later when a Rose Garden speech by the president reaffirmed opposition to quotas. But that was not nearly enough. Sununu called in White House counsel Boyden Gray and vice presidential chief of staff William Kristol, plus two outsiders: New Right legal activist Patrick McGuigan and former judge Robert Bork.

They devised language to cleanse the bill of racial quotas and ensure it would not spawn a plethora of lawsuits. That was what Sununu carried Friday to Kennedy, who agreed to staff meetings to study the changes. In polite language, Sununu was challenging the senator and the civil rights movement: Do you want a bill or a veto?

Whether this is just a bluff was addressed by Sununu to us Friday shortly before he left for his appointment with Kennedy. ''The {civil rights} label itself is insufficient for presidential signature,'' he said. ''It must be a real civil rights bill. It cannot be a quota bill.''

The impact of the arts controversy is more limited, but the notion of the president condoning taxpayer funding of obscenity is even more absurd than of his embracing quotas. Bush, eschewing the know-nothing label, is loath to tromp hard on Frohnmayer, viewed by White House aides as a self-promoting hero of the arts community.

The NEA chairman sought to exploit the president's inclinations by sending him a handwritten letter. Frohnmayer painted himself as a foe of censorship, fighting off both ''left wing'' and ''right wing'' forces. Controlling obscenity, he told Bush, should be left to the courts.

That caused Sununu to name a three-man team -- Gray and Kristol (part of the civil rights rescue operation) and White House personnel chief Chase Untermeyer -- to protect the president's interests. Their intent is to identify Bush with moderate restrictions on arts funding such as House Republican Deputy Whip Steve Gunderson proposes.

In his private letter to Bush, Frohnmayer justified firing his senior deputy chairman, Alvin Felzenberg, on dubious grounds of administrative incompetence. More to the point, Sununu was upset with Frohnmayer's use of computer printouts to target Felzenberg, incorrectly, for leaking information to us. ''Mr. Frohnmayer has been told that that's not the right thing to do,'' he said.

Not funding obscenity ''doesn't mean you have to censor,'' Sununu told us. ''It means you have to tell the difference between right and wrong.'' That is not easy in Washington, making essential the chief of staff's mission to guard against well-meaning aides propelling a well-meaning president into political disasters.