All right, the people elected Ronald Reagan and a conservative Republican Senate and a conservative, nearly Republican House in order to jack up the nation's defenses. That's stipulated. Those who felt Jimmy Carter had come around to a sufficient appreciation of the nation's military requirements cannot be surprised if the Reagan forces set out to do what they promised they would in the national security field.

But that's too easy. The people's broad choice in defense may be for "more," but the people ae in no position to define the details. What the Republicans and like-minded Democrats have won is not simply a mandate for a new policy but the obligation to tackle anew the old defense question, "How much is enough?" Or, better, how much is enough for what?

In the recent Democratic years, much defense debate was skewed toward an ideological question: the legitimacy of the sue of power in a context of Third World turbulence and great-power strategic equivalence. That question seems noe to be behind us. The answer reflected by the political consensus is that the use of power -- call it war -- si legitimate. Certainly this is so of the prospect of fighting in the Third World. It is less so of the prospect of Soviet-American nuclear war, but even there the trend toward thinking the unthinkable -- preparing to fight a nuclear war -- is evident.

In the Republican years stretching ahead, the defense debate has some of what sort of Third World wars the country should be preparing to fight, and the even harder question of under what conditions the United States might contemplate nuclear war.

It's early. There are already some signs, however, that the GOP may start out by doing what it long accused Democrats of doing in respect to social issues: spending money. Sen. John Tower (R-Tex.), incoming Armed Services Committee chairman, indicated the scale the other day: add at least three billion real dollars to Jimmy Carter's $157 billion defense budget this year and go up to $294 billion in 1985.

I spoke with Tower later, and he suggested that this is what it woudl take to make up for the $240 billion by which he said the Soviet Union has outspent us in the last decade. He said the Pentagon had special costly missions like sea-lane control to perform, and the Amercian people would simply have to decide "whether they want to settle for inferiority."

But I don't think this is the end of it. With due respect to the diplomatic signals sent and the domestic reassurances provided by increasing the defense budget, it's not enough. At a certain point -- at least by the second year, when the military increment starts to get very big and the Republican Party's now-substantial civilian constituencies start to get very demanding -- Reagan will come under pressure to show that he's spending those extra billions on the Pentagon for cause.

So it is scarcely too soon for the Reagan wave to start asking some of the hard questions. For instance, should the United States be preparing not merely to contest Soviet-sponsored aggression in the Persian Gulf region but actually to match Soviet power there? This seems to be the intent of many in the new Republican leadership, and it has a certain appeal. But the dollar and political implications of deploying near-equivalent American power that close to the Soviet border have barley begun to be explored. As the Reagan people grasp them, surely they will have to ponder whether it would not be just as well to put more emphasis on supplements to conventional military power, like diplomacy and energy conservation. Otherwise they may be drawn to the logic of strategic thinkers like Robert W. Tucker of Johns Hopkins University, who argues -- in the November issue of Commentary -- that American weakness in the Gulf now compels Washington to consider tactical nuclear war.

Similarly, what will be the budgetary, strategic and political results of taking Tower's advice to push ahead on major strategic systems that would otherwise be on the table in a resumed SALT negotiation? He wants essentially to make sure that no significant part of American security is mortgaged to achieving succes in arms control. I think this is one of those superficial pseudo-tough formulations that savvy hawks like John Tower ought to be able to demolish in a trice. Weapons- and mission-oriented conservatives of this school should be the first to see the value of restricting the hardware available to the other side.

Brave formulas hatched in the political wilderness and clench-jawed avowals of the need to assert national will no longer suffice. What will the Republicans do now that they don't have Jimmy Carter to kick around anymore?