It was soon after the Six-Day War. I was coming out of the main hall of the Knesset, after making a speech calling for the immediate establishment of a Palestinian state.

Another Knesset member came down the corridor - a nice person, a Labor Party man, a former bus driver. Uri, he said, catching me by the arm, what the hell are you doing? You could make a great career! You are saying many attractive things - against corruption, for the separation of religion and state, about social justice. You could have a great success at the next elections. But you are spoiling everything with your speeches about the Arabs. Why don't you stop this nonsense?

I told him that he was quite right, but I couldn't do it. I didn't see any point in being in the Knesset if I could not speak the truth as I saw it.

I was elected again to the next Knesset, but again as the head of a tiny faction, which was never going to grow into a strong parliamentary force. The man's prophesy came true.

In the course of the years I have often asked myself whether I was right then. Wouldn't it have been better to give up principles, even for a short time, and win political power, without which it was impossible to realize them?

I don't know if my choice was right. But I have never felt any remorse, because it was the right choice for me.

I REMEMBER this conversation when I hear about Barack Obama. He is facing the same dilemma.

There is, of course, one big difference. I was heading a very small faction in a very small country. He heads a huge party in a huge country. Nevertheless, the nature of the political dilemmas is the same in all countries, big or small.

Politics is, as Bismarck said, the "art of the possible". It demands compromises. The politician is a professional, not so very different from a carpenter or a lawyer. His job is to put together majorities for enacting legislation and taking decisions. To achieve this, he has to make compromises. Some do this easily, since, in any case, principles are not really important to them. But for people of principle, it can be very hard.

So what is the place of principles in politics? Must a politician sacrifice some principles in order to realize others? And if so, where is the limit?

THIS DILEMMA becomes even more acute in an election campaign.

In the course of my political life, I have conducted five election campaigns for the Knesset. Four I won, one I lost.

These days I follow Barack Obama's campaign, follow and understand, follow and get angry, follow and worry.

I listen to what he says, and I understand why he says it.

I look at what he does and often get angry.

I see him walking a tightrope across an abyss, and I worry.

I saw him performing before the Jewish lobby, where he broke all records for fawning, and I asked myself: What, is this the man who will bring about the Great Change?

I heard him speaking enthusiastically about the right of citizens to bear arms, including Uzis and Kalashnikovs, and buried my head. What, Obama?

I heard him supporting the death penalty, a barbaric punishment that positions the US somewhere between Iran and Saudi Arabia, and did not believe my ears. Obama???

I seems that Obama is moving further away from himself with every day that passes - and we are still at the beginning of the main election campaign.

I CAN just imagine the discussion at Obama's staff meetings. There he sits, surrounded by strategists, pollsters and PR people, all of them great experts, at the top of their professions.

Look, Barack, one of them is saying, these are the facts of life. The liberals are with you anyhow, you don't have to win them over. The conservatives are against you, and nothing will change that. But in between there are millions of voters, who will decide the outcome. These you must attract. So don't say anything unusual or radical.

You must tell them the things they want to hear, the second chimes in. Nothing that smells of hard-core liberals, please. We need the votes of rightists and evangelicals, too.

Anything definite will push away votes, a third insists. Every principle will upset somebody, so please don't go into details. Just stick to vague generalities which appeal to everybody.

I have seen many candidates, both in Israel and the US, who started out with a clear and incisive program, and ended up as blurred, boring and faceless politicians.

IN GOETHE'S great drama, Faust sells his soul to the devil for success in this world. Every politician has a Satan of his own, who offers power in exchange for his soul.

You have principles, this Satan whispers in his ear. They are very nice, but if you don't win the elections, they are good for nothing. You can realize them only if you come to power. So it's worth giving up some principles, making some compromises, in order to win. Afterwards you will be free to do whatever your heart desires.

The candidate knows that this is true. In order to fulfill his plans, he must first of all be elected. To get elected, he must also say things he doesn't believe in and give up things he does very much believe in.

And the question is again: Where is the limit? Which concessions are permissible on the way to the aim? Where are the red lines?

The Devil knows that the small compromises will lead to larger compromises, and so on, on the slippery slope to the loss of the soul. Without the candidate noticing, he is sliding downwards, and when he opens his eyes, he finds himself in the filthy political swamp.

This is the first big test for the aspiring leader: to know the difference between the permissible and the forbidden. Between the "art of the possible" and the "end justifies the means". Between the stubborn insistence on his principles and the total surrender to those experts, who turn every new program into a mishmash of empty phrases.

SINCE THE beginnings of democracy in Greece, it has been bedeviled by a question: can the people, the demos, really be relied on to make the right choices? How can the public choose between different solutions for problems of which they have no real understanding? After all, the millions of voters lack even the most rudimentary knowledge about matters of the budget, the complexity of foreign relations, military strategy and the thousands of other matters that a head of state has to decide about.

The answer is: indeed, they have no idea. One cannot demand from a cab driver, a dentist and even a professor of mathematics to be cognizant of Afghan tribes or the international oil scene. So representative democracy is unavoidable. Here the electorate has only one thing to judge by: the perception of leadership qualities.

How do people decide that a candidate is a "leader"? Is it a question of self confidence? Strength of character? Charisma? Physical appearance? Success in previous tasks? Do they believe that he or she will indeed fulfill their election promises?

These days it is not easy to get a true impression, because the candidate is surrounded by a large group of "spin doctors" who manipulate his image, put words in his mouth and stage-manage his appearances. Television is not a modern edition of the ancient Athenian agora, as it is claimed. It is by its very nature a mendacious and falsifying instrument. Yet in spite of everything, it is the image of the candidate that is decisive in the final count.

Barack Obama has impressed millions of citizens, especially the young. After years of moral decay under Bill Clinton and the power-obsessed folly of George Bush, they are longing for change, for a leader they can trust, who has a new message. And Obama has a wonderful talent for expressing this hope in uplifting speeches.

The danger is that when the edifying speeches dissipate, they will leave behind no leader with the character, the strength and the talent to fulfill the promise.

If Obama surrenders to his advisers and to the Satan whispering in his ear, he may gain votes from the other camp but lose his credibility, and not only in his own camp. The public may decide, instinctively, that "he hasn't got it". That, after all, he is not the leader one can trust.

On the other hand, if he is not prepared to make the necessary compromises, if he repels too many voters, he will be exposed to the opposite danger: that he will be left with his principles but without the ability to realize them.

He is facing four grueling months. The temptations are many, on either side. He must decide who he is, how much he is ready to give up without betraying himself.

And perhaps he must follow the example of Charles de Gaulle, who assumed power as a man of war and used the power to make a difficult, almost unbearably painful peace.

I DON'T want to be what Yiddish derisively calls an etzes-geber, from the Hebrew word for advice and the German word for giver. A person who proffers advice without taking any responsibility and without paying any price.

Even if I were asked, I would not presume to give advice to Obama, the candidate for the most powerful office in the world.

Apart from the advice given in "Hamlet" by Polonius to his son Laertes: "This above all: to thine own self be true!"