Inside Ronald Reagan's organization there are growing concerns that neither the candidate not the campaign may be up to the rigors of a tough presidential contest.

The concerns are as numerous as the graffes that have dogged the Reagan campaign in recent weeks. Some say that campaign director William J. Casey just is not up to the job. Others complain about the growing bureaucracy at the Arlington headquarters, about insufficient support for Reagan on the campaign plane or about inconsistent communications with key congressional supporters.

Increasingly, however, the growing, persistent concern of a few knowledgeable supporters is about what one of them delicately calls "the human factor" -- meaning the mood and condition of Reagan himself.

"Ron's either tired or uptight," said one who is close to him, in evaluating Reagan's recent performance. "He's in a different kind of contest now -- a Presidential contest with a capital P. And he seems to be having the first-quarter jitters, or at least I hope that's what they are."

What sparked this oservation was Reagan's Labor Day comment in Detroit that President Carter was "opening his campaign down in the city that gave birth to and is the parent body of the Ku Klux Klan."

Many saw this as just another Reagan slip, on the order of his confused statements about what U.S. policy should by toward Taiwan or his reference to the Vietnam war as "a noble cause."

But this slip was qualitatively different than the normal Reagan gaffe. Through two campaigns for governor and three presidential contests, Reagan has made his share of oral slips. Rarely, if ever, however, has he slammed a campaign opponent.

Though Reagan has been described as everything from a know-nothing ex-actor of a bombastic ideologue, his campaign style has been to respond to slurs with trace and good humor. In 1976, his aides complained during the early primaries that it was difficult to prod Reagan into critizing Gerald Ford's record, much less he man.

Reagan's departure from the norm has provoked a variety of explanations from those who are close to him.

Some say that Reagan was merely tired after a long day of campaigning in hot, humid weather. They observe that most of Reagan's slips come, as this one did, when the 69-year-old candidate is near the end of the day, and suggest that he can be scheduled more judiciously.

One aide says Reagan really doesn't are for Carter, considering the president mean-spirited man. He suggests that his feeling came out when Reagan inexpertly tried to contrast his campaigning or blue-collar votes in Detroit while Carter was bolstering his political base in he old Confederacy.

And still another Reaganite suggests that the candidate, who has been carrying his won campaign all year, is being sent but on the trail with very thin staff support.

On the Labor Day trip, for instance, Reagan was unaccompanied by any member of Congress. His wife, Nancy, whose political acumen is highly respected on the Reagan plan, was campaigning for her husband in New York. Chief of staff Edwin Meese, who often travels, was back in the Arlington headquarters.

One of Reagan's problems, a friend points out, is that the candidate has relatively few congressional friends. Reagan's friends tend to be non-politicians who can't provide whatever is the missing ingredient on the campaign.

The exception to this rule is Sen. Paul D. Laxalt of Nevada, a close friend and one of the few people credited with talking to Reagan in plain language about his problems. When Laxalt was aboard for an extended period during the 1976 primaries, Reagan enjoyed one of his most trouble-free periods of campaigning.

Laxalt, the campaign chairman, plans to travel as much as he can durning the weeks ahead.

But Laxalt has his own reelection campaing to worry about. And he rejects the notion that "giving Ronald Reagan a keeper" is likely to solve the problem.

The person who some would most like to see on the campaign plane is Stuart Spencer, who was along yesterday on Reagan's trip to Jacksonville and New Orleans. Spencer is one of Reagan's first campaign consultants, and was the political director for Ford in 1976.

Spencer, who is tough, blunt and politically astute, has been slowly working his way into the inner loop of the campaign since he was brought on as an adviser at the Republican National Convention. He is not eager for the high visibility of constant travel with the candidate, but a each stop he is able to give Reagan a political briefing that few others seem able to provide.

One source of campaign slipups -- the use of "noble cause" comes readily to mind -- is that Reagan's speech texts have rarely been circulated to a wide circle of advisers in advance. The insiders who saw the phrase "noble cause" had heard Reagan use the remark in private converstion, and didn't react to it in the speech text.

Rep. Thomas B. Evans of Delaware, a key House supporter, said that this problem has been corrected and that congressmen are now getting a look at the Reagan texts. Casey lunched with Evans yesterday in an effort to improve what once seemed to be promising relations between the campaign and congresstional backers.

But none of these correctives is likely to mean very much unless Reagan settles down and reemeerges as the smooth, effective campaigner who won the Republican nomination in a walk after a disastrous beginning.

There was some upturn of optimism at headquarters yesterday, after two straight Reagan days without any new mishaps.

There is no evidence, at least so far, that Reagan's mishaps have caused any precipitous decline in the polls.

Republican pollster Robert Teeter said yesterday that his surveys do not show any Reagan decline. Reagan pollster Richard B. Wirthlin said that Reagan is still ahead in the organization's latest survey.

There were scattered reports of organizational dissatisfaction, especially in the South. Jean Sullivan, the Republican national committeewoman from Alabama, approached an aide to George Bush in Jackson, Miss., on Wednesday, and urged that either Reagan or Bush go to Alabama as soon as possible.

Reagan has other priorities right now.

Ever since he fired campaign manager John P. Sears on the day of his New Hampshire primary victory, Reagan has made it known taht he didn't want any strong man running his campaign. The prevailing view in Arlington is that Reagan has succeeded in this goal beyond his wildest expectations.

"The governor is going to have to tighten up," says one well-placed Reagan aide. "We can't make Jimmy Carter the issue if we make ourselves the issue. aWe can't whine because the press is covering our slipups -- and we blow Reagan's goodwill with the press if we do. We can't continue to be considerate about staff slipups. The governor has to discipline himself and demand the same of his staff. If he wants to win, he has to take effective charge of his own campaign."