So Mrs. Thatcher won a resounding victory in Great Britain, and has a 142- seat parliamentary majority that will allow the Iron Lady to pursue a rigid program of public spending cuts and a further shift from public to private ownership of industry.

The favorite parlor game of the moment is to try to decide what meaning the British election has for us. Does it help her fellow conservative, Ronald Reagan? Does it hurt anyone with a liberal image, like Walter Mondale and by the same token help John Glenn? Does it mean that high unemployment is defused as a political issue, so long as inflation has been whipped?

There is a temptation among observers to answer all such questions in the affirmative. Joseph Kraft thinks there is "an unmistakable message to the Democrats": unemployment and its effects on society won't help beat Reagan.

David S. Broder agrees that the dramatic drop in British inflation had much more impact among voters than the 13 percent unemployment rate, given the assurance that welfare-statism will take pretty good care of those out of work.

But it should also be noted that what happened in Great Britain was as much an expression of British voters' disgust with the Labor Party as anything else. The Conservatives got substantially less than a majority, only 42 percent of the popular vote. The Liberal-Social Democratic Alliance--the new third party-- got 25 percent of the popular vote, or within a hair of Labor's 28 percent, while minor parties got 5 percent.

In other words, 72 percent of the voters were against Labor, compared with 58 percent against Thatcher--and that's why she won big.

Reagan, as a 1984 candidate, isn't likely to enjoy the benefits Thatcher derived from a third party. John Anderson is threatening to run again. But last time out, although he made a respectable showing for an American third-party candidate, he got only 7 percent of the vote.

It is therefore too easy to look for a duplication of the British results here. The Democrats for the moment do not have strong leadership, nor has the party settled on a cohesive alternative to Reaganomics. But the Democratic Party is not a union-controlled party, nor is it an extreme leftist party, nor is it in a state of disarray. The congressional elections of 1982 would suggest that it is very much alive, and there is no reason to think it cannot unify behind a candidate selected at next year's convention.

Nor has the American economy suffered like the creaking, antiquated British industrial structure. According to OECD data, for the three years to mid-1982, real growth in Britain declined by about 5 percent, while on the average it rose 2 percent in the rest of the OECD area, including the United States.

The United States hasn't even been hit so hard on the inflation front. At its worst, consumer inflation in the United States touched an annual rate of around 13 percent, and has now come down to about 4 percent. When Thatcher arrived in May 1979, the British retail price index was rising at a 12 percent rate. That shot up to 22 percent within a year, and now, in response to the crunch of recession, it's also down to 4 percent.

As bad as inflation was here, it was a lot worse for the average British citizen --who didn't have the private savings cushion of most American voters. So relief on the inflation front was clearly dramatic. It makes sense that Britons worried that transferring power to a leftist, inflationist Labor Party might send prices skyrocketing again.

But there's no reason to think the American voting public will view things in just the same way. And in any event, I'm not sure that the American voter will be disposed to view progress on inflation as an undiluted blessing so long as interest rates are sticky (mortgage rates, for example, are still too high) and unemployment flirts with the 10 percent level.

For all these reasons, one shouldn't read too much into Thatcher's victory. The cutting edge for Reagan, assuming that he's going to run--and assuming the American public won't be whipped into a jingoistic fury, as the British were over the Falklands--will still be the total direction of the American economy.

If economic activity is perking up, and unemployment has drifted below 9 percent toward 8 percent or less in the summer of 1984, Reagan ought to win handily--even if inflation is moving back up.

But if Reagan is still running a Thatcher-type economy in which the cost of a low level of inflation is continued high unemployment--especially among blacks and Chicanos--we are talking about a different ball game in which the British lesson doesn't apply. In that circumstance, the public here should be able to find a Democratic alternative, a luxury the British public didn't have with Labor or the new Alliance.