Diversity in Dallas

President Reagan's popularity and the prosperity issue have been unifying factors for the Republicans: Like the weather pattern that has trapped Dallas in intense heat for days, they have sapped the GOP convention's appetite for combat.

But it would be a mistake to assume that the Republican delegates have suddenly come under the spell of an unaccustomed conformity. They haven't.

True, they declined to step up to making some decisions crucial to the party's future. A proposal to reapportion delegates more closely along state population lines went down to defeat before reaching the floor. The current system awards a fourth of all delegates as bonuses to states for various feats, such as having carried the state for the ticket in the last election; this skews the nomination race heavily toward Western, less populous states. It means that again in 1988, the more conservative GOP candidates will have the advantage; big states in the Midwest, plus Florida, Texas, and California - all critical in a close election - will have proportionately less influence in choosing the next nominee.

And the party platform does reflect the more assertive stance of the party's ideological right.

Yet there's more diversity of opinion at the convention and within the party than meets the eye in Dallas.

Consider that half the delegates who attended the convention in 1976 were Gerald Ford supporters, the other half Reaganauts. Or that George Bush, Mr. Reagan's 1980 rival, who still seems to take more accommodating positions than his chief, is the favorite of conventioneers to succeed Reagan.

Note that, whatever the President's own views and what the platform might say , nearly 60 percent of the delegates oppose an anti-abortion constitutional amendment. The same three-fifths majority supports a nuclear freeze - again in contradiction of the platform and the President's own stance. A third of the delegates favor the Equal Rights Amendment. Half would oppose sending troops to El Salvador to enable US-backed forces to survive. Half favor the Moral Majority; half do not.

Diversity lives among Republicans, too. There is unanimity in Dallas about Reagan's leadership, and almost as strong agreement that the economy is in good shape. But there is disagreement about almost everything else: about spending less on domestic programs to reduce the deficit, about spending more for defense.

What this suggests is that the contest to succeed Ronald Reagan, and even his effort to govern in a potential second term, must still take account of the variations in GOP outlook that are papered over for the moment in the celebration of Reagan's renomination.

The hard right has captured neither the Dallas convention nor the advantage for 1988. A survey profiling the Dallas delegates, by I. A. Lewis for the Los Angeles Times, shows the Dallas enclave divided into three main camps - a little more than half calling themselves ''somewhat'' conservative, and about a fourth on either side of them identifying themselves as moderate-liberal or as very conservative. Nationwide, the GOP is evenly divided between liberal-moderates and conservatives.

All this helps explain why those with ambitions to succeed Ronald Reagan - moderates George Bush, Howard Baker, Robert Dole, and conservatives Jack Kemp, Lewis Lehrman, Newt Gingrich - are feeling happy about their prospects. There is still enough diversity among Republicans for them all to appeal to. No one narrow profile anticipates a natural heir to the Reagan political legacy.