Pat Robertson's impressive showing in the Iowa caucuses did not spark universal jubilation among the nation's evangelicals. It's a good bet that after Iowa voted, the unhappiest man in Virginia was the fellow who not long before had been the dominant evangelical in our national politics and who had prominently endorsed the very candidate Robertson vanquished, Vice President George Bush. That's right, Rev. Jerry Falwell.

Falwell is now enduring this year's version of the embarrassment suffered in 1984 by two leading Democratic mayors who are black, Coleman Young of Detroit and Wilson Goode of Philadelphia, when they supported Walter Mondale and then had to watch Jesse Jackson's campaign become a crusade among black voters.

So where do the Robertson voters come from? Like many Americans, most hunger for moral values in our country. In part they represent the only partner in the Reagan coalition whose agenda was ignored. The Reagan allies who wanted their taxes cut got their taxes cut, just as the Reagan allies who wanted the defense budget doubled got their wish. But the folks concerned about pornography and abortion and interested in school prayer were forgotten. The Republicans disregarded their voices and their views.

More than a few Democrats are openly elated at the potential discomfort and disunity a Robertson insurgency could cause the GOP. There's a rough justice in that prospect. The Democrats would do well to meet the Robertson voters who in Iowa contradicted most pigeonholing.

According to The New York Times-CBS News exit polls, the Robertson supporters were predominantly in the younger age groups. Robertson won 40 percent of the votes of union members and the members of union households. His support came from the less affluent in attendance; nearly two of five voters earning less than $12,500 a year supported Robertson, while only 7 percent of those earning more than $50,000 picked Pat.

On election night, Robertson was a blue-collar candidate, and the profile of his support bears a striking resemblance to people once known as working-class Democrats. If they can suspend their chortling, Democratic strategists might ask themselves why these Americans are no longer Democrats.

Robertson's success led to the reappearance of one Big Fib of politics. This Big Fib holds that whenever a new candidate brings previously inactive people into active politics, all older candidates feel compelled to lie about how thrilled they are with the new people. Politicians have a tough enough time staying in office with a semistatic electorate. New people constitute an unknown and a possible threat to the established political order. The politicians feel they have to pretend that the newcomers are welcome.

In casting large public issues in moral terms, Robertson is simply honoring an American tradition. The American politician who borrowed from the Gospel of St. Mark to tell us that "a house divided against itself cannot stand" was Republican Abraham Lincoln, and it was Democrat Franklin Roosevelt who announced that "the money-changers have fled from their high seats in the temple of our civilization."

The United States in the final analysis is an ideal. It is not a market. What makes us unique and the object of the world's admiration as well as envy is not our capital formation but our values. One of our most admirable values (which Robertson has occasionally forgotten) is our commitment to pluralism, equality and tolerance.

And although the Robertson constituency is primarily motivated by cultural and moral values, economics does play a role. Based on the Iowa sample, these are working-class Americans, most of whose children go to public schools, who are more apt to depend on the safety of public transportation and the security of public playgrounds. Drugs can poison their neighborhoods; crime can touch their families. Teen-age pregnancy and pornography are not unpleasant abstractions but real tragedies.

At the Holy Trinity School in middle-class Beaverdale where Precinct 17 Republicans caucused stood Angie Gipple, an attractive and animated woman. Next to her was Don Bothwell, who could have been a finalist in any Robert Mitchum look-alike contest. Bothwell looked a lot more like a ladies' man than a Robertson man, and not long ago one might have thought that this couple from the middle class would have voted for the Democrats. But Bothwell explained his presidential choice for Robertson simply by gesturing affectionately toward Angie: "She's my girl; it's as simple as that." Remember, stereotypes not only die hard. They are also often wrong.