A new, carefully controlled and virtually isolated Ronald Reagan has made his appearance on the campaign trail.

He is a candidate who holds no news conferences and is kept far away from reporters, lest they overhear some stray, self-damaging remark. His ad libs at rallies are kept to a minimum for the same reason. He is kept well rested, either starting his campaign late in the day or ending it before sunset.

The aim of Reagan's strategists, and they make no secret of it, is to prevent the Republican presidential nominee from saying anything that might detract from his anti-Carter message and become the news of the day.

Sometimes, even under the most controlled campaign conditions, this is not easy.

On Sunday evening, for instance, Reagan was in Philadelphia at the field house of St. Joseph's College addressing a group of Republican volunteers.

Before launching into his party pep talk, Reagan observed -- as he has in the past at private institutions -- that President Carter opposes tuition tax credits. Then, Reagan said, "His [Carter's] newly created Department of Education is planning all manner of things to limit and restrict institutions of this kind because their faith is totally in public education only."

No one present, including anyone on Reagan's staff, knew what he was talking about. Nor was there a Reagan spokesman available to speculate.

Fifteen hours later, while Reagan was breakfasting with Philadelphia's Cardinal John Krol, campaign spokesman Lyn Nofziger told reporters that Reagan had two things in mind. The first, he said, was that any new department justifies its existence by adopting restrictive regulations. Nofziger said Reagan also was referring to an ongoing study, which he did not otherwise identify, in which the government would become responsible for higher education acreditation.

Reagan's schedule reflets the dual decision to keep the candidate both under wraps and well rested.

Reagan had a free morning Sunday and will have another Tuesday before his long-awaited economic speech to the International Business Club here. Today, a relatively busy one with three public events in Kokomo, Ind., and Chicago, he concluded his campaigning by 5 p.m. and then had a private dinner with Gerald Ford.

While Reagan's aides are limiting access to the candidate, they are trying to give a different picture of what is going on to the outside world. Reporters are kept away from the candidate, but all of the network television crews are allowed at every "press pool" -- events normally limited to the wire services and a single representative of the different types of news media. As one Reagan aid put it succinctly, it is "pictures that count."

But there are some in the Reagan entourage who are uncomfortable with this conclusion. They know that the campaign Reagan is running is likely to recall the successful Nixon presidential campaigns in 1968 and, especially, in 1972.

"Reagan is no Nixon," observes one aide. "The governor is a much freer and independent man, and he feels bound and restricted at times by some of the fetters which have been placed on him for his own good."

Some are reminded of the campaign in Iowa last January, when the candidate's exposure to voters also was limited even though he was much more accessible to the press than he is now.

Reagan lost the Iowa caucuses. He then changed his strategy and won a smashing victory in the subsequent New Hampshire primary when he became the most accessible of candidates.

Throughout much of 1980, Reagan has remained a relatively open candidate. But the current game plan does not call for him to be accessible again.