"The nation cries out for desperate leadership," declared a New York radio personality last November as he introduced Ronald Reagan on the eve of the former California governor's entry into the presidential race.

That slip of the tongue has been recalled more times than once by Reagan's changing cast of advisers as the candidate himself has struggled to demonstrate he has the intellectual capacity and knowledge to be president.

In the first week of his campaign, Reagan fumbled questions about federal assistance to Chrysler Corp. and the city of New York so awkwardly that those who heard him thought he knew very little about either issue. Last week, he gave a similar impression on the issue of agricultural parity.

Such statements continue to fuel doubts about Reagan even as he marches triumphantly through the early primaries. What emerges is the seeming paradox of a candidate who can out-debate rivals in candidate forums and outmaneuver contentious reporters in press conferences, yet still kindle questions about his intellectual capacities.

In political circles, the old question about Reagan -- Is he too conservative to be elected president? -- has largely been replaced by another: Does Ronald Reagan know what he's talking about?

The reason is found in the kind of answer Reagan gave a weekend ago in Wichita, when a farmer asked him if he would support 100 percent of parity.

"I wish I could answer the question for you. That, I know, is a technical question, 100 percent parity," Reagan replied. "I have to confess to you I am not as familiar with some things as that."

When a reporter repeated the question later, Reagan said that he may know more about parity than he had indicated. The reporter persisted, asking just what did he know.

"I don't know enough about it to fully discuss it," Reagan said.

Reagan sometimes fumbles on matters that are much less complicated than farm parity. In an effort to demonstrate that he can appeal to Democratic voters, Reagan has been saying that he won the California governorship in 1966 by 1 million votes and was reelected "by nearly as many" in 1970. His majority in 1970 was 497,000 votes, with most of the smaller margins in Democratic precincts.

Other Reagan statistics are intriguing but difficult to check, such as his 1976 claim -- repeated several times in this campaign -- that there are more white-tail deer in this country now than existed in George Washington's day.

And there are questionable statistics, attributed to a nonpartisan source, such as Reagan's claim "The General Accounting office listed 41 separate items of waste and fraud in government totaling $11 billion. That's $11 billion a year that could be eliminated right away."

There is no such GAO report.

The figures are taken from a Republican congressional study, which in turn took most of them from a report compiled by the inspector general of the Department of Health, Education and Welfare. This HEW report says that $2.7 billion of the $7 billion of estimated fraud and waste in HEW could be eliminated under existing law.

Likewise, Reagan frequently says in his campaign speeches that the potential oil available in Alaska exceeds the proven oil reserves of Saudi Arabia. He attributes this information to the U.S. Geological Survey, which currently estimates that there are 9 billion barrels of proven oil reserves in Alaska and a potential of 49 billion barrels more, compared with 165 billion barrels of proven crude reserves in Saudi Arabia.

Reagan's statement is based on a report by Commonwealth North, an Alaskan pro-development group. This report quotes two former Alaska governors, Walter Hickel and William Egan, as saying that their conversations with geologists led them to believe the total potential oil in Alaska, both onshore and offshore, ranges from 300 billion to 600 billion barrels.

Reagan's sometimes fuzzy answers and occasional, misplaced statistics are apparently due to several things, including bad briefings by his staff or even no briefings on a subject. In other cases, they reflect Reagan's lack of specific knowledge about various issues on which he should be better informed. In still other circumstances, Reagan's apparent ignorance appears to be merely a candidate's way of dodging a question he doesn't wish to answer.

To some degree, the issue of Reagan's intellect has dogged him throughout his political career. He once accused the University of California of "subsidizing intellectual curiosity."

In his first campaign for governor, the opposition portrayed him as a know-nothing actor reading from a prepared script. When Reagan took office, reporters and legislators made bets about how often the new governor would say "I don't know" during any given press conference.

But Reagan came to understand the workings of California's mammoth state government and learned how to use its levers of power. The point is relevant to present questions about Reagan's competence, because he has suggested that he would operate the presidency the way he ran the governorship -- by relying on the judgment of experts he trusts and taking decisive action based on their recommendations.

An example that reflects this attitude and the generality of Reagan's knowledge is contained in his comments on the need for a U.S. strategic deterrent. Throughout the campaign, he has criticized President Carter for canceling or delaying various U.S. weapons systems, including the MX missile. Yet, at the same time, he has said that the race-track deployment system of the MX favored by the administration is "unworkable."

In a foreign policy speech in Chicago on March 17, Reagan had this to say:

"To prevent the ultimate catastrophe of a massive nuclear attack, we urgently need a program to preserve and restore our strategic deterrent. The administration proposes a costly and complex new missile system. But we can't complete that until the end of the decade. Given the rapidly growing vulnerability of our land-based missile forces, a faster remedy is needed."

Reagan said afterward that he did not know what this "faster remedy" should be but would consult a variety of experts about the issue. Sometimes, on the campaign trail, he has suggested that the United States needs an anti-ballistic missile. Other times, he has pointed with alarm to the development of Soviet civil defense and said that the United States should do more civil defense planning.

There are times when Reagan's supposed ignorance masks attempts to avoid difficult political questions. On the parity issue last week, Reagan -- as he now acknowledges -- was trying to keep from telling a farmer that he doesn't favor 100 percent of parity (a 1910-1914 formula for farm price supports), without saying so in as many words.

"I didn't want to say a flat 'No,'" Reagan said. "I certainly wasn't going to say a flat, 'Yes.'"

Reagan had good reason to dodge the question, even though he did so in such inexpert fashion that some thought he had never before heard the word "parity." In 1976, during an Illinois primary that almost knocked him out of the presidential race, Reagan had campaigned on the "philosophical" position that farmers should not ask the government for help.

"You subsidize the inefficient when you put a floor under the market price," Reagan said in Danville, Ill., on March 8, 1976.

No one questioned Reagan's clarity then, least of all the Illinois farmers who heard his message and voted for Gerald Ford. This time, in the farm belt, Reagan has opted to be more political and less clear.

Sometimes, however, Reagan gets carried away by the desire to tell audiences what they would like to hear.

The most striking example of this in the 1980 campaign came in Miami's Little Havana district during the Florida primary, when Reagan was asked by an anti-Castro journalist what he would do to stop "harassment" by the Carter administration of Cuban refugees opposed to Castro's regime. Reagan promptly denounced this "Harassment," even though he couldn't give a single example of it to reporters who approached him after the press conference.

One of the oddities of the Reagan campaign is that the candidate operates almost alone, with the help of a young researcher on the campaign trail much of the time, even though he can draw freely from a variety of experts for research on his major policy speeches.

"No campaign has ever given a candidate less support in the field than we've given Reagan," says a key Reagan political operative. "Half the time the candidate isn't briefed, or isn't briefed by a political person, or is briefed so badly that he knows little more than the name of the town in which he's speaking. He's going well because people trust him and like the direction in which he's heading. But his campaign hardly helps him at all."

One of Reagan's charms is that he can always come up with a statistic, usually lots of statistics, to make a point. He uses so many of them that it has been said he never met a statistic he didn't like.

"Twenty-seven agencies enforce 5,600 regulations imposed on the steel industry," says Reagan. "U.S. Steel is closing 17 plants. . . . We once produced 45 percent of the world's supply of steel; that is now 19 percent. We once built 76 percent of the world's automobiles; that is now 38 percent. And General Motors has to employ 23,300 full-time employes to comply with government-required paperwork. Standard Oil of Indiana keeps 636 miles of computerized records demanded by the Department of Energy, which can't produce a single quart of oil."

Once a statistic finds a haven in a Reagan speech it generally stays there despite the best efforts of aides and reporters to dislodge it. This is the produce of Reagan's photographic memory, which stores a lot of information but often doesn't discriminate about the quality.

The factual content of his speeches may aggravate experts, but Reagan's political communications may be effective, regardless. Voters who find themselves agreeing with his sentiments may not need to know whether his statistics are absolutely correct. They understand his point, and they like him.

Reagan is accessible on the campaign tail, and reporters who interview him for the first time often are struck by the apparent spontaneity of his answers. Only later do some of them realize that they have been hearing verbatim sections from one of his basic speeches.

Reagan probably couldn't change this if he tried. He has been broadcasting, performing or speaking, in one form or another, for nearly 50 years, and has been his own researcher much of this time. He once said that he hadn't had a real private life since he signed a Warner Bros. contract in 1940.

A Republican officeholder who has known Reagan for a long time and is now among his leading supporters agrees.

"There isn't any private Reagan that I know of," this Republican says. "You punch the tape recorder, and the cassette plays. This used to bother me because politicians are, as you know, usually much different in private than they are in public. But I've gotten use to Ron making a speech at me when we're alone. At least with him, what you see on the stump is what you get."