THERE SEEMS to be no doubt that some people did not vote on Election Day because the outcome of the presidential race was known so early. The polls were still open in most states when television began to proclaim Ronald Reagan a landslide winner and still open in many states when President Carter conceded defeat. Because of those two developments, especially the concession, some voters left the lines in which they were standing, while other voters never bothered to make the trip to the polls. Their votes, they decided, didn't matter.

They were right, of course, so far as the choice of president was concerned. But they may not have been right about the other votes they would have cast. There were a handful of congressional races and even more state legislative races in which the ballots of these discouraged voters might have made the difference.

This was a clear and unfortunate effect of television and radio coverage of legitimate news events on the election process. But it was a phenomenon that could be minimized in future elections by either Congress or the state legislatures. There is, after all, nothing sacred about the hours or even the days when polling places are open.

In California, for example, some politicians are talking seriously about opening polling places for a few hours on the evening before Election Day and then closing them on Election Day about the time the polls in the eastern states are shut. There is also the idea, which has been kicking around for some years, that Congress should proclaim a 24-hour voting period ending, say, at 10 p.m. eastern time; each state could decide which hours during that period its polling places would be open, except that all of them would close simultaneously.

Both ideas are worth consideration -- the California plan, of course, would not be fully effective unless other states altered their hours also. And both are preferable to unworthy suggestions that the results in early-closing states be suppressed for several hours by either election officials or the news media. Suppression by state officials would be an invitation to fraud and vote-stealing; voluntary suppression by the news media would be a practical impossibility, and compulsory suppression would be unconstitutional -- and a terrible idea to boot.

In company with the electoral college, the traditional dates and hours of presidential elections have not been changed to meet the conditions of modern life. They should be before the year comes along when the early returns from the East discourage enough potential votes in the West to change the ultimate result.