Opponents of Ronald Reagan are beginning to be bolder in their talk about his being too old for the presidency. He is nearing 70. A fit age, it is said, for an elder stateman but not an active one.

No one makes the senility charge outright. The elderly might be offended, for one thing, and everyone knows that aging is relative, for another. Some people are "old" at 50, while others, like spunky Claude Pepper, the Florida Democrat, are full of kick at 79.

The strongest argument against Reagan is not his age, but his staleness. He offers few fresh ideas. In the past few years, I've sat through a half-dozen Reagan speeches. Each was the same. His thoughts about "faceless bureaucrats," the evils of "Washington red tape" and the virtues of businessmen have been on the Reagan shelf for so long that even the pull-dates have expired.

For a while, I thought that judging Reagan by his speeches was perhaps unfair. At banquets and dinners, all politicians serve up their favorite applause lines. They telegraph the code words the audience came to hear and then wrap up the gab with a call for a new America.

But even in print, the staleness of Reagan's mind is overpowering. In an interview in the current issue of Politics Today, he tells of being impressed with Jimmy Carter during the 1976 campaign: "But since then, (Carter) has made a 180-degree shift in his policies. He's gone with the liberal line completely."

Completely? That will come as news to the Americans For Democratic Action, the group of liberals that began the Dump Carter movement last spring. If anyone should know about the purity of the liberal bloodline, it is the ADA -- and in affidavits piled as high as the Capitol Dome it swears that Jimmy Carter never was a liberal and certifiably isn't now.

At times, the president's politics are ones that Reagan himself champions. Carter's grain and technology embargo against the Soviets fulfills the get-tough posture that Reagan spoke of in the Politics Today interview. Alluding to the Russian troops in Cuba -- a current issue when the interview took place -- Reagan said: "Now it seems to me that within the first hours when it was confirmed that the brigade wa there, the president should have said to the Soviet Union, 'Look, detente is a two-way street; this is an affront to us and there will be no further discussion of trade with you until those soldiers are back in the Soviet Union.'"

This is largely what Carter did after Russian troops invaded Afghanistan. But Carter acting like Reagan wasn't good enough for Reagan. Last week, he announced his opposition to the president's embargo.

When Reagan tries for some fancy footwork, he ends up tripping over himself. Since 1972, he has been attacking the Occupational Safety and Health Administration as the enemy of the hapless businessman. In the Politics Today interview, Reagan is at it again.

The agency's "thousands and thousands of regulations" are not only harassing God-fearing factory owners, but "there has been an increase in the number of accidents under OSHA."

At the agency itself, no one knows where Reagan gets his figures. Nor is it known where he gets his terms. "The number of accidents" is a meaningless measurement, an official explained. An accident can be a mere interruption of work. In the measurements that do have meaning -- death, injury and illness -- the rates are decreasing. Since 1972, the first full year of OSHA, fatalities have dropped from 5,500 to 4,590 in 1978, even though the workforce is larger. The rates of death, injury and illness per 100 fulltime workers has gone from 10.9 in 1972 to 9.4 in 1978.

In battling OSHA, the liberals, or whatever, Reagan likes to come on as the hard-punching conservative. Which he is -- except that he's punching at air.