Can the Republicans lose?

Our better newspapers and newsmagazines have been full ever since the Democratic convention of learned treatises on the subject of whether the Democrats can win and, if so, how they should go about it.

Most of this discussion, it seems to me, misses a main point about politics in any democracy. With rare exceptions elections are not won by opposition parties clamoring for a chance to run the country. They are lost by a party in power failing to satisfy a majority of the electorate.

The United States is no exception to the general rule. People in the US go to the polls, not to vote the outs in, but to vote the ins out after the ''ins'' have either by acts of commission or omission or accidents lost the confidence of a majority of the voters.

The outs have two true functions in this political process. It's up to them to make sure that the public is informed about the fumbles and failures of the party in office, of which there are always many. And they must be ready to take over at any time when the party in office has run out of steam, or made some dreadful mistake, or in any way done disservice to the country.

The 1980 election was almost a classic case in point. Jimmy Carter was defeated after two essential conditions for a change of party had occurred. Confidence in the competence of the Carter team to govern was undermined by a series of damaging developments and failures.

The economy did poorly. Inflation and unemployment remained too high for comfort. The promising Camp David process for peace in the Middle East went nowhere. The American Embassy in Iran was seized and its people were held as hostages. The attempt to rescue them failed. The Russians invaded Afghanistan.

As election day neared in 1980, the Carter team in Washington appeared to be made up of well-intentioned people who did not seem to be up to the job. They behaved like amateurs in government, which, indeed, many of them were.

When the voters of midsummer four years ago looked over to the other side to size up the Republicans as a possible alternative government, they were at first uncertain. Ronald Reagan had for too long sounded too much like a swashbuckling cowboy champion of the rich bent on doing in the poor orphans and widows.

But Mr. Reagan adjusted his image during the campaign with enormous skill and success. More and more he was seen as a friendly good guy out to save the pennies of the thrifty and hardworking from the grasping fingers of ''welfare cheaters.'' His manner was easy and comfortable. He learned to reassure, instead of frighten. By election day, people felt that their future would be in friendly hands if they elected Ronald Reagan.

That is the way it works. The voters will vote for a change if and when the party in office appears to have become incompetent to govern and the party in opposition seems to be a safe alternative.

The Democrats are working at the duties of an opposition party. They are calling attention to the mistakes and failures of the party in office - of which there are several. And they are presenting themselves as a plausible alternative.

But there is one thing the Democrats cannot do. Only the Republicans can produce the failure that would cause the bulk of the voters to begin to think they might want a change.

So far the Republicans have enjoyed remarkably good fortune. The economy prospers in spite of the budget deficit and high interest rates. The Russians have not invaded anywhere. Since the withdrawal from Lebanon, no American soldiers have been shot at in other people's wars.

The Republicans can lose by misfortune, accident, or stupidity. So far they have avoided serious accidents and major folly. There may be a day of reckoning ahead for their deficit. But voters in a democracy seldom look beyond election day. They vote on today's condition, not on tomorrow's consequences. Democrats cannot manufacture a Republican stumble, folly, or accident. They can only hope, and be ready if one happens.