The most striking thing about Gary Hart's conduct in all the furor over his candidacy this year has been his defiant, almost angry denial that the matters of personal character, integrity, temperament, habits and behavior are relevant to the presidency. It is an attitudehe displayed before his withdrawal from the race last May and is taking now with a vengeance in his second incarnation of the year.

As his former pollster, Paul Maslin, noted, Hart considers that a "trivial" part of the presidency, something used by politicians, reporters, consultants and other insiders who want to get between Hart's "pure message and the American people."

Thus the former senator from Colorado, while apparently considering himself uniquely qualified for the office of president, delib-erately chooses to ignore -- indeed, to scorn -- much of the basic symbolic nature of that office.

It is a strange contradiction. For the vote for president is the most personal one Americans cast. Congressmen are reelected to a great extent for doing their constituent case work. But the presidency is far more than that, or than any other public office. It's far more even than selecting the person we trust with the nuclear arsenal.

The American presidency as created by the Founding Fathers is unique. After long debate, in which they seriously considered some sort of symbolic monarchy on the grounds that the people needed, or at least wanted, something of the sort, they wound up lumping everything into one office. As a result, the president is not only the prime minister and chief executive, but also the embodiment and symbol of the nation's values, ideals and aspirations.

Hart made a pedantic bow in this direction in his announcement when he said the president "must become the nation's first teacher to help our people understand some very tough problems and how together we can solve them."

That's certainly part of it, a big part, but the office is much more than just being a sort of big university lecturer in the social sciences. The president has to translate those ideas into reality through political persuasion, and the source of his power is his ability to convince the people that he will promote their hopes and values because he shares them.

Hart doesn't seem to understand this. What drove him out of the race last May was serious evidence of womanizing. He talks of it now, as he did then, as a "mistake," which he implies was a one-time transgression that he regrets and for which he has done penance.

People in some parts of the country have a different word for it -- "cheating." It is a word heard often in country and western songs about infidelity. The fact is that the Miami Herald undertook the surveillance of Hart's Washington town house last spring in the context of years of rumors about his peccadilloes; no news or political organization with an ounce of sense has even dreamed of staking out the homes of, say, Richard Gephardt or Michael Dukakis.

The fact also is that Hart lied to his supporters last spring when he was specifically asked about such activities. Lying and cheating are serious charges against anyone, and it is not sensationalist or irrelevant to examine them closely in a presidential campaign.

Hart presents himself as a private man, which in many ways he is, and as concerned with substantive issues, which he certainly is. On "Nightline" Tuesday night, when asked whether he might not lack the moral authority to lead the nation, he responded: "If I had been behaving, if you will, immorally -- flaunting my behavior in public -- or if I had been conducting myself in public in ways that didn't require some surreptitious surveilance to find out the possibility that I might be involved with someone else, then I think that case could be made."

He apparently has forgotten about the color photos of him and Donna Rice in Bimini. That didn't require any surreptitious surveillance, and if allowing a camera in the room under those circumstances isn't "flaunting" such behavior, it comes pretty close to it.

Gary Hart got a whopping 49 percent negative rating in ABC's Tuesday/Wednesday overnight poll. Studies of political polls,particularly one done by Lee Atwater, Vice President George Bush's chief political strategist before he got into politics full time, indicate that when a politician's negativesgo above about 35 percent, it's fatal. It may take some time, but it's almost inevitably fatal.

According to those close to him, Hart got back in the race because he couldn't stand being on the sidelines and out of the na-tional debate. There aren't many who think the presidential candidate game as he plays it will ultimately yield him any more gratification.

James R. Dickenson is a political reporter on The Post's national staff.