When morning flatters the mountaintops on Wednesday, March 9, voters may not know what they did the day before. Democrats who vote on Super Tuesday may determine only the person who would be a Democratic administration's choice as U.S. representative at the United Nations. Republican voters may think they are deciding who shall seize the reins of the ''Reagan Revolution,'' but the most they will determine is who will wear the straitjacket that Reagan policy has tailored for the nation.

On Super Tuesday, while Dukakis, Gephardt and Gore go ''cherry picking'' (targeting particular areas), Jackson will begin bringing in his sheaths of delegates. Whether or not a Democrat arrives at the Atlanta convention with a lock on the nomination, Jackson will have to be paid. What can he want from a Democratic administration? As representative at the United Nations he would, because of his political clout, enjoy virtual immunity from being fired, an airplane in which to roam the world and a work place where the specialty is his specialty: talk.

Al Gore is the other Democrat whose day, if he is to have one, is supposed to be Super Tuesday. But even Democrats who have a crush on him, and who are not economical of encomia, show when they give vent to their emotions how dyspeptic Democrats are feeling.

In an editorial that is impossible to read without giggling, The New Republic, a Democratic magazine, has thrown its weight behind Gore. His ''spontaneous speech is both vivid and allusive.'' With some of his vivid allusiveness he makes ''the sciences of the next century his special concern.'' Timed to tip the Super Tuesday balance, the magazine's Dixie readership is offered an arresting vision: Gore understands not only the threat to the ozone layer but also the fact ''that technologies like fiber optics are the key to . . .''

Actually, the real case for Gore is less lyrical but more concise: he alone among Democratic candidates is not a foreign-policy naif. That's it. No need to drag in fiber optics.

The New Republic paints warts-and-all portraits of Gephardt and Dukakis that are a dermatologist's dream. The ''cold comfort'' one can take from Gephardt's ''reckless agenda'' of ''crude populism'' and ''ugly'' and ''deluding'' xenophobia is this: his record of flip-flops indicates that any professed belief of the moment is just a ''marketing tool'' that must take a terrible toll on ''the sinews of his identity.''

Turning to Dukakis, The New Republic says his ''rigidity'' represents neither deep conviction nor great passion, only an ''overweening estimate of himself.'' If Dukakis believes something, ''this suffices as evidence of the rightness of the belief. No arguments, please.'' Aren't Democrats fun when they fight?

Aren't Republicans clever when they duck -- responsibility, that is. They have devised the ultimate ''southern strategy.'' With the Reagan administration's new budget, the Republican Party now stands for the Scarlett O'Hara approach to governance: let's think about problems tomorrow.

Seven years ago the party stood for two disciplines -- strong defense and balanced budgets. The new Reagan budget, which calls for the fourth consecutive year of real decline in defense spending, makes Reagan the trillion-and-a-half dollar president: that will be his cumulative deficit. In the history of the republic before him, the total deficit was $914.3 billion.

If the new budget is enacted, defense spending will have risen 87 percent under Reagan, but spending generally will have increased 61 percent. Because of the political choices posed by Reagan's deficits -- ''wheelchairs or tanks'' -- this is probable: when the fiscal decade 1981-91 is done, the growth rates for defense and general spending will have converged.

Seventy percent of the budget consists of defense (declining), interest (soaring), Medicare and Social Security. Under Reagan, spending on Medicare and Social Security will have risen 115 and 67 percent, respectively. As the population ages and expensive medical capabilities multiply, government will become even more of a machine transferring wealth from young to old.

Under Reagan, interest payments as a percentage of the federal budget have more than doubled to 14 percent. The fiscal 1989 budget envisions interest payments of $151.8 billion, more than the combined budgets of nine departments -- Agriculture, Commerce, Education, Energy, Interior, Justice, Labor, State, Transportation. The biggest change in the budget during the Reagan years is the enrichment of a rentier class -- those who live in places like Grosse Point and Riyadh and rent their money to the profligate U.S. government.

This regressive transfer of wealth is an issue made for a conservative populist, a hawk on the deficit. But can Bob Dole expand his message beyond that ''one of us'' slogan? We will know by the time that morning flatters the mountaintops.