IS GEORGE BUSH afraid to meet his opponents in debate? Certainly not, say his backers. The reasons he's been turning down invitations from William F. Buckley Jr. to appear on "Firing Line" with other Republican presidential candidates is that, uh, he's not a declared candidate yet (never mind that he spent $1 million on last year's Michigan precinct delegate elections and has raised a total of $9 million), or, hmmmm, that the process is beginning too early (though he's been speaking out in recent weeks on education, farming and the Iran-contra scandal) or, gee, the schedule is just so cluttered that he can't make Mr. Buckley's date of Oct. 28. What's happening is that Mr. Bush, ahead in the polls, is happy to travel across the country and appear before large audiences without sharing the spotlight; and his rivals are squawking. Should anyone else care?

Yes. You may moan that the campaign is beginning too soon, but the dates have been set, and Americans will have to choose presidential nominees between January and June of 1988 from two fields full of candidates they know little to nothing about. The more chances they have to see them in unrehearsed action, the better. The first debate in this presidential campaign, between Democrat Bruce Babbitt and Republican Pete du Pont, took place in Des Moines May 29. All the Democratic candidates squared off on the not entirely friendly ground of "Firing Line" July 1 in Houston. Most of the candidates will have been debating for seven months before their first contest. Mr. Bush has agreed to two debates, Dec. 1 and Jan. 8, before his first contest, plus three more before Super Tuesday March 8.

This suggests a Bush strategy of lying somewhat low before the first contests, all of which take place on terrain perilous to him, in the hope of coasting through to the more favorable ground of the southern and big northern state primaries. But a strategy that serves the short-term interests of candidate Bush may not serve the voters. Mr. Bush is better known than his rivals, but not known in depth. Voters will want to see more of him. They may remember that his performances in the Nashua debate with Ronald Reagan and the 1984 debate against Geraldine Ferraro in Philadelphia were not stellar. Mr. Bush ought to be there with Mr. Buckley on Oct. 28.