When conservatives were unhappy with political compromises during President Reagan's first term, they usually blamed pragmatists on the White House staff for leading their hero down the garden path of moderation. The belief that the president performed best when left to his own devices was summed up in the all-purpose slogan: "Let Reagan be Reagan."

Be careful what you pray for, it is said, for your prayer might be granted. Reagan now is being Reagan, and the true believers are learning more than they ever wanted to know about the perils of unleashing him.

White House chief of staff Donald T. Regan arrived promising to reinforce Reagan, and he has been true to his word. Communications director Patrick J. Buchanan promised faithfulness to a conservative agenda and is also keeping his commitment.

But no one at the White House now sees his role as preventing the president from making a fool of himself; Reagan is free to say whatever comes to mind about Social Security, South Africa, Central America or the SS.

Some would say Reagan has become more "ideological" now that he no longer faces reelection. But Reagan has long been a card-carrying conservative. His recent difficulties are more personal.

Up close, Reagan always has been more complex than his admirers or his detractors recognize. He is at once ideological and pragmatic, compassionate and insensitive, intuitive and uninformed. An aide says there were times in his first term when Reagan, angered by some news account, arrived at the Oval Office "about to go off half-cocked." Usually, he was saved by subordinates who protected the president rather than themselves. The first-term inner circle of chief of staff James A. Baker III, deputy chief of staff Michael K. Deaver and counselor Edwin Meese III had problems and feuds, but they were willing to make Reagan look good at their own expense. The new motto seems to be: "Every man for himself" or, alternatively, "It didn't happen on my watch."

In fairness, Reagan's scheduled visit to the Bitburg cemetery in West Germany where SS soldiers are buried came during a transition period in the White House and originally was the president's fault. Reagan always has believed that those who support his policies and share his jokes are solid gold. In his first term, he displayed a naive loyalty to such dubious appointees as Labor Secretary Raymond J. Donovan, the first U.S. Cabinet secretary to resign under indictment.

Reagan's horizons are now international, but he still trusts those he likes. The Bitburg blunder was basically the result of an impulsive agreement Reagan made Nov. 30 when visiting West German Chancellor Helmut Kohl emotionally asked him to join in a "reconciliation" ceremony. When Reagan has made unwise commitments in the past, he could be sure someone would extricate him. This time, there was no "someone." After White House spokesman Larry Speakes announced the visit, Regan took a wait-and-see attitude while the furor built. Predictably, it did.

Last week, Buchanan advised the president that "caving in" to protesters would be a sign of weakness. This form of argument might have appealed to Buchanan's one-time boss, Richard M. Nixon; it did no service to Reagan. Any president needs some protection from himself, and Reagan needs more than others. He is an above-the-battle president whose knowledge of any given subject is apt to be fragmentary. Often, he compensates with an uncanny ability to abandon mistakes and declare defeats to be victories.

Reagan always has been sensitive to anti-Semitism and the realities of the Holocaust. He was an early supporter of Israel, and his sentiments have remained unchanged as he evolved from Democratic liberal to Republican conservative. It is ironic that Reagan's cinematic view of history should be most heavily exposed on an issue where he has demonstrated both understanding and commitment. He is the president and deserves the blame. But he would have been less embarrassed if his current managers had recognized that "letting Reagan be Reagan" does not necessarily mean encouraging the president to do anything that comes into his head. Reaganism of the Week: Explaining to regional editors why he is persisting in planning to visit the Bitburg cemetery, Reagan said, "And this cemetery -- we only found out later, someone dug up the fact that there are about 30 graves of SS troops."