IF YOU'VE followed the letters to the editor on this page recently, you may have gotten the impression that the hundreds of people running for national office are ignoring the major question most of their constituents have been wrestling with: whose motor vehicle belongs in which lane of the highway?

The correspondence got going some weeks ago with a letter from a woman who complained of being tailgated by a large truck on the Beltway. This drew a heated response from another correspondent, who said the first writer was probably a "Left-Lane Bandit" -- that is, one who slowed traffic by occupying a passing lane. There followed a rebuttal, an apology and a lot of other letters on the subject.

Then John O. Nestor of Arlington entered the argument, and quietly raised hostilities to the level of the Thirty Years' War. What the previously unheralded and unsung Nestor said in his letter was that it was his practice to move to the passing lane, set his cruise control at 55 miles per hour and stay there for the duration of his trip.

In the days that followed, the increasingly notorious Mr. Nestor was challenged by one correspondent after another in terms that suggested he was some sort of Hitler of the Beltway or Stalin in a Sedan. The unrepentant Mr. Nestor wrote again explaining his position, and the flow of letters increased. This week it was suggested by one correspondent that the by now incredibly controversial name of Nestor become a standard term of treachery -- as Vidkun Quisling's was in another connection -- to be applied to those who accept his doctrine of driving.

What is all this about? It seems that the perhaps- soon-to-be-world-famous Mr. Nestor has not just violated -- that probably wouldn't be so provocative -- but has outrageously flouted the code of conduct of most American drivers. In some foreign places, a flashing of the headlights from behind will be politely heeded by the driver in the passing lane. In others there will be horn-honking, cursing, exchanges of obscene gestures. But in America, the strong, silent approach prevails. This consists of engaging the obstructing motorist in an unspoken suicide pact by driving about 5 feet behind him (when truck drivers do this, it is more on the order of a homicide pact), conveying a message something like this: Okay, friend, here we are bumper-to-bumper at 60 mph; do you move over or do we both go up in a fireball when somebody slows down ahead of us?

This technique is used by many drivers regardless of whether the car in front has anywhere to go to get out of the way. It is used in passing lanes, and sometimes by people who wish to pass in the right lanes. It is probably more obnoxious and dangerous, and certainly much more widespread, than the depredations of John O. Nestor and his trusty cruise control, and we're sure we are going to hear a great deal more about all this.