It was the first, and it will be the last. That's the conventional wisdom on Super Tuesday, the first regional primary in American electoral history, custom- designed by moderate southern Democrats to deliver one of their own into the White House. The plan was a flop, every commentator agrees: after all, doesn't a northern liberal, Massachusetts Governor Michael Dukakis, lead the delegate count? And isn't that Jesse Jackson in second?

The conventional wisdom is, as usual, dead wrong. Super Tuesday has made Tenessee Sen. Albert Gore, the Dixiecrats' hand-picked candidate, a virtual certainty for the nomination. And for dessert it has served up the Republican any Democrat would most wish to face in November: George Bush. Some flop.

Gore? How's that again? Isn't he in third? Yes - that's all he needs at this point. In fact, he'd win even without such a surprisingly strong showing as he turned in on Tuesday. All Gore had to do to lock up the nomination was to beat Richard Gephardt.

Here's how it plays out. Gephardt is finished. He has no money, and Gore has taken his momentum as the torchbearer of party conservatives.

The irony is that, on his record rather than his rhetoric, Gore is among the most liberal candidates in the race. He has been allowed to cross back and forth over the centre line as he pleases without having to declare his political baggage, while Gephardt was being strip-searched for opportunism by the press.

NO CHANCE

With Gephardt out, his support has nowhere to go but to Gore. Now it's a three- man race, with Gore the ''conservative'' against liberal Dukakis and far-left Rev. Jackson. That's how it will likely remain to the convention. Jackson has no chance for the nomination. So the key question becomes: in the back rooms of a brokered convention, who will Jesse Jackson throw his support to? Dukakis? or Gore?

On their record, there's little to choose between them ideologically. But Gore's more conservative positioning in the campaign gives him more room to make platform and patronage concessions to Jackson without marginalizing himself. The two men, moreover, like each other: at debates, they often wisecrack together like schoolboys while another candidate is speaking. Both are sons of the South. And Gore has support in the black community.

Dukakis can win only if he can take more than half the delegates into the convention. But to do that he must take two thirds of the remaining delegates, and even with his organization and abundant cash, that looks unlikely.

His only chance was to score a knockout on Super Tuesday, to prove a northern liberal could be a winner for the Democrats across the nation. Had he been able to roll from state to state, as before, he might have used the momentum from Iowa and New Hampshire to his advantage. But with Super Tuesday in the way, the Dukakis roll could not get up to speed.

Super Tuesday was a defeat, not a victory, for Mike Dukakis. Al Gore's southern strategy worked - because Super Tuesday was designed to make it work.