It took a little doing, but the White House last week managed to take one of President Reagan's longstanding and deeply held ideas and make it look like a quickie commercial for the next installment of "Star Wars."

The president deserves part of the blame because he was so afraid of word leaking out that his national security adviser, William P. Clark, and others in the National Security Council and the White House science office, didn't draw on the scientific experts in the bureaucracy who could have fleshed out the concept of a futuristic defense against Soviet intercontinental ballistic missiles.

But the blame isn't entirely Reagan's. The president was willing to be more specific than he was in his speech in terms of money and commitment, but opponents of the idea in the Defense Department argued against it on grounds that the technology wasn't sufficiently developed. This should have been an argument for delaying the speech, but instead it became a reason for taking all the juice out of it and making it sound like something the president had dreamed up after reading a science fiction comic book.

"There are some people who believed that the best thing about this program is that there is no specific program," one West Wing official said dryly when he learned of the president's speech a few hours in advance. "It's a vision, a conception."

In fact, it is a vision that Reagan has been groping for ever since the 1980 presidential campaign when he questioned the wisdom of a continued policy of "mutual assured destruction." Science adviser George A. Keyworth said that Reagan raised the issue with him in the early months of the administration, but that this never became a signal to create a policy.

Even though the administration has been spending $1 billion a year on research into laser and particle-beam weapons that could be used against missiles, no one tried to bring the various ideas together into a coherent package. As a result, the White House couldn't even keep its promise to provide reporters with a fact sheet on what was supposed to be one of Reagan's most significant proposals.

Reagan is right in thinking that the notion of a defensive system has more potential popular appeal than does mutual assured destruction. It's a pity that his important idea was tossed out in such a way that it both obscured his defense message and wound up looking like a Buck Rogers gimmick intended to take the sting out of his military buildup.

While the president was soaring from the 19th to the 21st century last week, his earthbound minions were struggling to get their dates straight.

It seems that somewhere in the bowels of the White House a proclamation had been conceived to honor Earth Day, which few Lou Cannon REAGAN & CO.have considered a joyous rite of the Reagan administration. White House spokesman Larry Speakes announced that the proclamation would be distributed to assembled reporters. Before this could happen, a quick check of the calendar showed that the architects of the proclamation had confused the vernal equinox with Earth Day. Back in the vault went the proclamation, ready to be issued on April 22. Perhaps they can rechristen the holiday "Lost in Space Day."

Headline of the Week (From the New York Post of March 24): "Star Wars Plan to Zap Red Nukes." Those who read the small type learned that the president was "introducing a new program to develop a galactic defense umbrella rather than first-strike nuclear weaponry." Wait until the empire strikes back.

Reagan is an inveterate telephone caller who consoles the bereaved and keeps in touch with critics through conversations from the White House. After Sara Fritz, U.S. News & World Report's White House correspondent, wrote an article about Reagan's calls, the president made another--to Fritz, praising her account and explaining that he had been making such calls ever since he was elected governor of California in 1966.

One of the first such calls he made, Reagan said, was to a couple who had written objecting to his proposal to charge tuition at the University of California. "Hello, I'm Ronald Reagan," he said to the woman who answered. "Yes, and I'm Bette Davis," she replied.

The word in the White House is that the president's upcoming environmental speech, the first of his presidency, will be timed to coincide with the Senate confirmation of William D. Ruckelshaus as the new director of the Environmental Protection Agency. For once, all the power brokers in the White House are marching in step with the president in support of Ruckelshaus, who returned to Washington with the compelling mix of self-deprecatory humor and dedication that marked his stay here when he was first administrator of the EPA during the Nixon administration.

Asked what his wife, the equally dedicated and outspoken Jill Ruckelshaus, thought of his decision, Ruckelshaus replied: "She thinks I ought to be committed." But he then launched into a vigorous defense of EPA's mission, saying, "People won't trust their government if it can't deal with toxic wastes." Reaganism of the Week (From an interview with Henry Brandon, retiring Washington correspondent of the Sunday Times of London): In discussing negotiations in the Middle East, the president said: "Sometimes they have been presented as one side asking for the moon and the other side offering green cheese. And then they talk their way to a point between these two extremes and settle it."