THE JULY 1 DEBATE among the Democratic presidential candidates on William F. Buckley's "Firing Line" in Houston was pretty interesting -- more so, in fact, than we had expected. You don't need to buy co-moderator Robert Strauss' statement that he had never been prouder of a field of Democratic candidates to agree that the thing went off well.

What viewers saw over PBS from Houston were usually well-informed, sometimes thoughtful, and often partisan discussions of the budget, trade, interest rates, the Strategic Defense Initiative, the 1986 tax reform law, energy, and Cuba and Nicaragua. Interspersed were 90-second videotaped autobiographies (some stiff, some smooth) and videotapes of each candidate telling a joke (Bob Hope is not in trouble). These may have been hokey, but they helped give voters a sense of the candidates as human beings and broke up what otherwise would have been a tediously long broadcast.

Who won? None of the candidates was uniformly brilliant or banal; each had his high and low points. The most dramatic moment was when Albert Gore took on Mr. Buckley over scientific panel reports on SDI. David Broder reports that a "jury" of 85 Iowa Democrats equipped with computerized rating devices rated Mr. Gore rather low and thought Richard Gephardt, Paul Simon and Michael Dukakis did best. Bruce Babbitt is supposed to have done worst, though he did well in his debate last month with Republican Pete du Pont. There will be plenty of time for these ratings to rise and fall. Even Iowans have seven months to make up their minds and will have more chances to see these candidates.

How would these Democrats do in a debate against George Bush, Bob Dole or one of the longer-shot Republicans? Not so badly, we'd guess. The 1984 general election debates let us see how well each of two familiar candidates could do in unrehearsed circumstances: Did Walter Mondale have a sense of command? Was Ronald Reagan still up to the job? In 1988, debates are needed to let us get to know candidates whom we know very little or not at all. "Firing Line" did a great service by presenting the Democrats in a revealing format, with results that were instructive. Now when will the Republicans -- in particular George Bush, who's been avoiding joint appearances -- accept Mr. Buckley's invitation?