Aside from the identity of George Bush's running mate, only one big question hangs over the Republican National Convention that convenes Monday in New Orleans.

Indeed, it's a query that hovers over not just the convention but the ensuing GOP presidential campaign as well.The question: How much can the enormously popular President Reagan do in campaigning for Vice President Bush without having voters focus on the wrong man and compare Bush to Reagan, rather than to Democratic nominee Michael Dukakis?

In other words, can Reagan's exceptional personal popularity be transferred to Bush without overwhelming him?

At this point, the Bush camp is understandably focusing not on the campaign but on the convention, where they have had trouble making up their minds about what constitutes the proper mix of Reagan-Bush appearances.

As recently as last week, Bush aides were saying they anticipated no meeting between the two men in connection with the convention, that they expected Reagan - who is to address the convention Monday night - would have left New Orleans before Bush arrives. That scenario would have let Reagan bask in the adulation of the delegates without detracting from Bush's own time in the spotlight.

But then some awkward questions started arising. Why couldn't the two men who together have led the nation for eight years at least encounter each other at their party's convention? Didn't they like each other?

White House spokesmen brushed aside suggestions there was anything unusual going on, saying the two see each other and consult frequently. Then, the Chicago Tribune reports, a new decision was reached: Reagan and Bush likely would meet next Tuesday morning at the Belle Chasse Naval Air Station outside New Orleans as the president is leaving for California and the vice president is arriving to attend the convention.

Apparently convention organizers decided it is better to risk having Bush overshadowed than to leave the impression that he and Bush are trying to avoid each other.

The challenge facing Bush is to emphasize his relationship with Reagan without appearing to be just a second banana. It's a challenge that is extremely difficult to accomplish, judging from the way presidential coattails tend to fray whenever a departing chief executive tries to pull his vice president into the Oval Office.

For example, Dwight Eisenhower did not provide the winning margin for Richard Nixon. Lyndon Johnson, as the New York Times recently put it, "was more a liability than an asset to Hubert Humphrey."

Can Ronald Reagan and George Bush break this pattern? Stay tuned, next Monday through Thursday, for at least some early indications of an answer that won't be completed until election day.

Likewise, stay tuned for the announcement of Bush's running mate, a decision that Bush is holding close to his vest in a deliberate effort to inject some suspense into the thoroughly-scripted affair. Tune in, too, for the discussion of the platform.

Though the Republican National Convention can be expected to produce little or no political bloodshed, it still deserves close attention. While some decisions that used to be made in the conventions are now made in the presidential primary elections, these proceedings are still part of the general national debate on public policy. Responsible Americans ought to follow closely what happens in New Orleans through the press and TV.