PRESIDENT REAGAN'S journey to the Capitol for the budget negotiations was an arresting piece of political theater. The scene brought to mind the similar negotiation at Tilsit in 1807, when, as you no doubt recall, Napoleon sat down to divide Europe with the king of Prussia and the czar of Russia. They chose a neutral spot for the talks--a raft, tethered in the middle of the Niemen River, which separated their armies.

The two cases are not exactly parallel, of course. The role of czar has never quite suited Speaker O'Neill. It is true that the treaties of Tilsit did not endure for long. They did not produce what the social workers call a stable living arrangement. But they held up for a few seasons--and that's more than you can say of the talks yesterday at the Capitol. The result there was a flat collapse, after six weeks of intense work that deserved a better ending. The negotiators seem to have decided only that an open disagreement was better than the faked and fudged quasi-agreement, with loose numbers and vague promises, that seemed to be emerging last weekend. In that, they are right.

There are a lot of people, both Republicans and Democrats, who will now have a strong interest in representing this affair as only another conventional partisan collision. In fact, it began with a challenge to the president from within his own party. Last summer, senior Republicans in the Senate began to warn the White House that its projected defense spending was too high, and its deficits too large. That row simmered through the fall, with the Democrats taking little part. When the president brought out his budget in February, congressional Republicans were stunned by the size of the deficits. They began working, with a good deal of support within the administration, to persuade Mr. Reagan that those deficits were too large to be tolerated. They persuaded the leaders of the House Democrats to join the talks. The Democrats agreed because they were hearing from home about interest rates, and the only way to lower interest rates is to lower the deficits.

But all of these maneuvers and discussions kept striking one intractable reality. Mr. Reagan sees no great need to change his budget. He thinks it's fine. He doesn't believe that it asks too much for defense. He thinks that the deficits are all right. And because he thinks those things, no deal has been possible.

Without any further change in policy, the deficit for the fiscal year 1983, starting in October, is likely to be about $180 billion--by far the largest, by any measure, since World War II. Congress will doubtless make some changes. But in the absence of the kind of explicit, comprehensive agreement that the late negotiations were seeking, any tax increases and spending decreases will be minor compared to that vast deficit.

At Tilsit, Napoleon, the king and the czar at least managed to get off the raft safely. At the Capitol, the barge sank, and by late afternoon the statesmen could be seen swimming rapidly for shore--all of them in different directions.