If judgment were oil, then, all by himself, Bryce Harlow would be OPEC.

Presidents Eisenhower, Nixon and Ford all brought that Harlow judgment to the White House. A couple of them even took some of his advice. Harlow has spent 11 of his 43 adult years in Washington working in the White House for a Republican president.

Lately, two Republican presidents -- Eisenhower and Ronald Reagan -- have been compared hereabouts. Can Reagan be another Ike, his personal popularity secure and separate from his policies and politics? Did the attempt on his life and his own admirable behavior throughout transform Reagan into an authentic national hero, immune from traditional political criticism? And, if so, who will be the Ezra Taft Benson and John Foster Dulles -- the "villains" -- of the Reagan administration? Will Malcolm Baldrige or Samuel Pierce join James Watt?

For an answer to this or just about any political question, Bryce Harlow is a consensus All-American of leading authorities. Harlow does see similarities between the two presidents.

"Reagan's for real," he said last week.

"He's a success, not at all insecure, free of hang-ups, and at peace with himself."

But is he politically another Ike?

"Not yet. By June 1953, the country had fallen hopelessly in love with Ike. When he stumbled, people picked him up and dusted him off," Harlow answered. "But it still could happen in Reagan's case."

A Persian proverb, heeded by generations of presidential assistants, advised that when the king says it is midnight at noontime, the wise man murmurs, "Behold the stars." Bryce Harlow never put much stock in Persian proverbs or in the contemporary celebrity of staff. Was Sherman Adams ever on the cover of People? His advice to all who will ever work in the White House or on Capitol Hill: "Never confuse yourself with your job. It may be important. You are not."

But Harlow did work closely with a lot of very important people. From 1941 to 1946, he was an army officer working with General of the Army George C. Marshall. Here are a few of his judgments about the men he has known.

Marshall: "Absolutely formidable personal character. Selfless to the point of being Christ-like." Harlow recalled Marshall's rigid sense of propriety when FDR told him: "George, I want you to call me Franklin." Marshall's response: "I'll try to, Mr. President."

Jerry Ford is cherished for his "tremendous decency." Richard Nixon's intellect is still respected. But one adjective to describe the resigned president: "driven." Ike was "the complete leader and politician."

There were no demons in Bryce Harlow's political world. He kept no enemies' list because he did not believe in enemies. Of all the politicians he knew, FDR and Ike were both "genuine naturals." He watched John Kennedy become a "natural." But to Bryce Harlow, Hubert Humphrey was "more of a natural than all of them -- Roosevelt, Ike or JFK."

Harlow, than whom there is no one better at the delicate art of White House-congressional relations, warned the Reagan people to beware of the incipient perception that the administration "does not care about the little people." That's what the Harlow antennae are beginning to pick up, and if that perception grows, it could be, he knows, the political kiss of death. The Social Security blunder did not help at all. Like Harlow's word, which you could always take to the bank, his judgment is still very reliable.

Harlow, who was an Oklahoma Democrat until the late 1940s, closed with an encouraging word of sorts for the members of his old party. He recalls that during the first year of Ike's first term, there was real disarray among Democrats then out of office for the first time in 20 years. His advice to the opposition: "Both parties will win again -- in spite of themselves."