Four Augusts ago, I suggested on this page that many Democrats were being too optimistic about retaining the presidency, that they were seriously underestimating the skills and appeal of Ronald Reagan. At the risk of being classified as a political contrarian, I would suggest today that Democrats are seriously overestimating Reagan's skills and appeal. In 1980 challenger Reagan could and did get the good of all his legendary assets, rhetorically singing, dancing and telling jokes with pleasure on the campaign trail. In 1984 incumbent Reagan can still sing, but he is finding it very difficult to dance, and dangerous to joke. Attention should be paid to that fact -- immediately.

My 1980 prognosis of impending disillusion for the Democrats was based largely on painful experience as a strategist for incumbent governor Edmund G. (Pat, not Jerry) Brown in 1966, when Reagan first ran for governor of California and won a landslide victory. But as George F. Will noted recently, Reagan's margin when he won reelection as governor in 1970 was only half that of his initial victory in 1966.

To put my theory about Reagan in 1984 up front and bluntly, I think he already looks much less formidable as a defender than he was as a challenger four years ago. I think his strategists, who are very astute, recognize the potential problem whether Reagan does or not, but that Walter Mondale and his strategists have only begun to see and exploit it. That does not mean Reagan can't or won't win. There is a lot more going on. But the Democrats have a much better opportunity to scrape away that famous Teflon coating in the next two months than many pundits or politicians yet understand.

And it is not just the generic problems of incumbency, but the bad match of an aging Reagan's indifference to facts with a campaign for reelection that offer the greatest opportunity to his challenger.

How are the campaigns of 1980 and 1984 different for Reagan? First, four years ago he had the unpopular and inflexible Jimmy Carter to run against. There was John Anderson, a significant independent candidate, to scoop up voters who were not available to Reagan himself but who regarded Carter as too much or too little to take. Such people find it either a pleasure or a duty to vote, but would as soon send a message as decide an election.

There were the even more numerous eligible nonvoters who don't much like taking an hour or so out of their busy private lives to perform a public function, especially when it means choosing between imperfect alternative candidates not up to their own fastidious civic standards. Yes, and there were also immediate issues in the summer of 1980, a host of them about which many voters had strong, unappeased emotions. American hostages in Iran, Russians in Afghanistan, an inflating economy still suffering from oil and other shocks, and tense confrontations over social and cultural values and behavior that had religious overtones. For a challenger with Reagan's skills and appeal, that was Marlboro Country.

What does he have in 1984? Well, he doesn't have Jimmy Carter to kick around any more and no great success to date in a strident, obvious effort to make Mondale look like Carter. Mondale has his own imperfections, but they are not much like Carter's. Reagan doesn't have John Anderson going for him this year either. And while there are still a lot of habitual nonvoters, the numbers and makeup of that population appear to be changing through mobilization of many of the women, minority group and maybe union members within it -- largely because of displeasure with the Reagan administration, its actions and its policies.

The overall issue situation is much cloudier and more difficult to assess, and probably won't be clear until we know whether the campaign comes to focus on the relatively placid surface of the present or on the potential for future turmoil gathering beneath that surface.

There is nothing immediate to produce great emotion on either side except the Ferraro candidacy. The Marines in Lebanon are dead, not hostages. (Think of what challenger Reagan would have made of that.) The Russians have quite understandably decided that negotiating with Reagan on arms control is useless, and incomprehensibly eased him halfway off the hook by appearing even more intransigent on the subject than he.

The economy looks to help the incumbent, but that is far less certain than is assumed. The expanding sea of debt -- private even more than public -- which buoys it is also leaking into the national hold in a way that ought to make the markets much more nervous than they already are. We are taking on water by the barrel and talking about bailing with teacups. That could mean terrible trouble next year or the year after -- or tomorrow. The Reagan team, ever alert, consequently is already inveighing against the purveyors of doom and despair even before anybody but Mario Cuomo has sounded the tocsin.

We are no closer to consensus on social and cultural change either in behavior or values, and indeed seem, if anything, more firmly polarized than ever. But Reagan and his "feeling good about America" clearly has made most Americans feel less guilty about the unfairness of a world we are told we never made, and for which we therefore cannot be held responsible.

What does this view of the differences in the circumstances between 1980 and 1984, some of which cut one way, some another, make in the potential effectiveness of the Reagan skills and appeal this fall?

First, his performance as a cheerful, likable personality whose flair for simplicity and anecdotal evidence in public discourse makes him a great communicator is an asset that will be enhanced rather than diminished, unless . . .

The unless is crucial. Unless he has to give specific answers to hard, even complicated questions on issues linked to his performance. Unless he is not permitted to shrug away errors and gaffes merely by changing the subject. Unless he is put on the defensive and kept there.

In 1980 the Carter campaign effort was to make him seem a threatening personality without much hard evidence and against the public's visual impression of him, especially in the one winner-take-all debate. That didn't work then and won't work now. In 1984 any successful effort will have to make what he now has done or not done be the hard evidence on which to judge his future behavior, base the charges and ask the questions, not once, but again and again.

That is not only reasonable but feasible, both in general terms and in terms of the specific concerns of large segments of the population. There were the Marines' deaths in Lebanon. There is the deepening involvement in Central America. There is the failure at least to work some things out with the Russians, especially on nuclear arms control. There is the blithe commitment to unbridled capitalism, which took us through a deep recession for those who could least afford it into a prosperity certain to founder in a floodtide of unprecedented debt.

That debt, not yet allocated either among the living or between the present and the future, is no longer just implied by Reagan's 1980 positions. It is a reality with which even many Republicans who didn't go to Dallas agree we must reckon by future massive sacrifice or suffering.

And, even more specifically, there is the outright rejection in action rather than in platform words of the aspirations of women and minorities, of the poor, disabled and otherwise disadvantaged. The challenger's jocular indifference to conservation and pollution in the 1980 campaign remarks about the dangers posed by redwood trees has been turned into the hostility of major acts of both commission and omission by Watt, Gorsuch and their less flamboyant successors in service to the incumbent.

In all these arenas and more, there is the opportunity to turn the non-threatening personality of the challenger into the person of an incumbent who has cheerfully done more damage to identifiable beneficiaries of government action than either his detractors or admirers in 1980 could have dreamed he would achieve. No wonder he felt good, even Olympian, about America as he looked out at the beaming, prosperous Republican convention, smilingly distanced himself from its ambitious platform for even more of the same and happily contemplated the pundits' advice to the Democrats not to attack him personally

The advice is probably half right. His personality should not be attacked, for it is not an issue. His personal views of the world, are, however.

His record and his responsibility for what it portends and the documented actions of his administration are what can be attacked successfully. So can his conduct and that of his staff and appointees and supporters.

If he can be brought to defend them, the evidence to date indicates he is not knowledgeable, adept or skillful. Reagan no longer has the luxury of dismissing descriptions of what he is about, as in his 1980 debate remark,

"There he goes again." Or as in his almost interminable press conference pleas that he simply can't understand why women, minorities, peace-seekers, the unemployed, poor, disabled, environmentalists, the aged, bankrupt farmers and small businessmen, union members, state and local governments and all the rest don't really understand how much he has done for them, how much he has their interest at heart -- not to mention his protests that he knows no statistics that support their complaints. This time the references will be to events or figures not lost in old California archives but retrievable from national memory and detailed in national news clippings.

As we have approached the onset of the fall campaign, Reagan's assurances and protestations have had an ever hollower ring, as if he weren't quite convinced of his own credibility except in set speeches before partisan audiences. As a challenger, even as a president, he has until now had the advantage. The press could ask questions, but it is not and should not be its role to attack. Now the campaign gives equal visibility to a credible attack and focuses public attention on the issues raised.

Now that he is officially renominated, the incumbent Reagan can no longer get away with telling the press that "we have to do something to hold down these second questions" as he retreats from the presidential podium back into the corridor of power. Neither in press conferences nor in debate can he avoid confrontations in situations he cannot control, where his ad libs are subject to tough analysis and his foibles subject to discussion.

Most of informed Washington of whatever political persuasion has a lower opinion of Reagan's capabilities and leadership than the public yet knows, has more private reservations about his failures of understanding and concern than it has voiced publicly. That includes the press. But only an opposition candidate in a campaign can voice them, even demonstrate their truth in the give-and-take of a debate. The press, already recognizing their validity, can then treat them seriously if further persuasive evidence is mustered in their support.

Can this happen? Not if Mondale and his strategists believe that it is impossible to get at Reagan as personally as Reagan and his strategists are trying to get at Mondale. Not if the Mondale campaign is conducted as if Mondale were the incumbent who has to explain and defend what happened before Reagan instead of going after what happened with Reagan and can be expected to happen again in a second term.

Curiously, Democrats have a terrible penchant for making their own candidate, rather than the opponent, the issue, especially if the opponent is riding high in the polls. Further, it is by no means certain that the Mondale campaign has the capacity and the sheer force of energy and will to make sure that doesn't happen again this year.

I think Mario Cuomo's keynote address to the Democrats was a great success, not primarily because of his special eloquence but because he understood all this, understood the vulnerability of Reagan's public persona and standing and went after it without fear or favor. Mondale's one gambit on taxes may not have been terrily wise in symbolic terms, but it seems to have rattled Reagan more than one could have expected because it made him defensive, made him explain himself in detail in a way that produced visible personal discomfort and uncertainty.

The fact is that with the exception of his happy week at the totally worshipful Republican convention, Reagan has not looked or sounded like the Great Communicator since the Democratic convention. Even at the GOP convention, he was more cheerleader and denouncer of Democrats than eloquent, convincing spokesman for his cause.

Nor, it should be added, has Mondale looked or sounded like Cuomo, or added any more unsettling challenges to the one he himself laid down at the convention on taxes. Even Mondale's response to Reagan's so-called joke about bombing the Soviet Union was feeble, and without the resonance or bite to require a personal Reagan rejoinder. It's as if Mondale's strategists thought that Reagan could deal with the consequences better than they, and therefore let him get away without dealing with it.

Geraldine Ferraro has had other things on her mind, and, for that matter, on Mondale's, but that is no excuse. If Mondale doesn't believe he can win by attacking Reagan as vigorously and unambiguously as Cuomo did, then he probably can't win at all.

If Mondale is willing to get as tough about Ronald Reagan as he did about Gary Hart, it can be an interesting campaign, and possibly even a winning one, but time to do that is already running out at a rapid pace. The "New Realism," a defensive slogan if I ever heard one, can wait. It's already time to lay down the artillery barrage and follow it into the enemy's trenches.

There is an old political axiom that declared that in order to win a political campaign, you have to give the voters either a show or a fight. It is clear who can provide the best show. That leaves no choice for the Democrats. They will have to provide the best fight. And Reagan looks like a defender who might not be able to go 15 tough rounds.