"I'VE BEEN RICH and I've been poor," Mae West is supposed to have said, "and rich is best." The same conclusion might be echoed, in candid moments, by Lewis Lehrman and Mark Dayton. Mr. Lehrman, the Republican-Conservative candidate for governor of New York, and Mr. Dayton, the Democratic-Farmer-Labor candidate for U.S. senator in Minnesota, have each spent about $7 million on their own campaigns so far, and each will probably spend a few million more by Nov. 2. They can do this, despite campaign finance limits, because in 1976 the Supreme Court ruled that expenditures by candidates on their own campaigns are a form of freedom of expression protected by the First Amendment, and cannot be limited by law.

Now, money isn't the only thing, but it sure helps. Mr. Lehrman, who urges major tax and spending cuts, is running even in the polls with his Democratic-Liberal opponent, Mario Cuomo, in liberal Democratic New York. Republicans with similar platforms in Ohio and Michigan, without such personal resources, are running about 10 percent behind. Mr. Dayton was not given much of a chance of defeating popular Republican Sen. David Durenberger, but he was only 4 percent behind in recent polls. Democratic challengers with similar platforms but less net worth lag far behind popular Republican senators in states such as Missouri and Indiana and Pennsylvania.

There is little evidence that voters resent candidates for such spending. But of course other politicians do, and they have a point: rich candidates have an edge. Until the Supreme Court decision, something was being done about it; even now, it might make sense to exempt candidates whose opponents spend large sums of their own money from some of the campaign finance law's limitations. But it would still help to be rich: Sen. John Heinz (R-Pa.), who spent $2.6 million on his campaign in 1976, has spent none of his own money this time because he doesn't have to: his wealth as well as his popularity deterred strong opponents from running against him.

Of all the ills afflicting the political process, the advantage that the few very rich candidates enjoy is not the most grievous. It is unfair for such candidates to have an advantage, but nobody guaranteed Sen. Durenberger or Mr. Cuomo an easy ride. In the long run, the political process is helped, not hurt, by robust, even if not entirely fair, competition.