Decision comes easy to those prepared to vote the national mood. The times are sour and Reagan the obvious agent of change.

But those determined to assess the national interest find a murky choice. Bad as conditions may seem under Jimmy Carter, they could become worse.

Reagan, to be sure, has emerged from the campaign the bigger man. He is genial when the president is mean, and reassuring where Carter is grim. His ignorance of detail does not compare unfavorably with his rival's mastery of the trivial. Especially since Reagan seems to know what he does not know.

The former governor of California has never tried to do everything himself. He was a 9-to-5 men in Sacramento. None of us who followed him on the campaign trail kneeled over from exhaustion. He would come to the White House acknowledging what he has already called "the limitations of the presidency." His prospects in office would depend importantly upon those around him.

In domestic policy, he has shown a commendable readiness to broaden scope. To the hard knot of far-out ideologists, he has added during the campaign persons of rich experience and strong common sense. George Shultz, Alan Greenspan and Arthur Burns are economic advisers of high caliber. It seems possible Shultz would go into the White House as chief of staff and deputy president -- a notable boost for a Republican leader whose ability to govern turns on harmonious relations with labor, the academic world and a Democratic Congress.

On the national security side, Gov. Reagan has recently been talking more with the likes of Henry Kissinger and Alexander Haig. The forced retirement of Richard Allen as chief foreign policy adviser, while a personal misfortune, eases their access even further. For the most part, however, Reagan has stuck by the hard-liners in his original entourage. His published statements, and his impromptu remarks, emphasize a passion to kill deader than dead the pending arms control treaty with Russia. While he talks loosely of a stronger military stance, he has yet to show the promise of a policy for dealing safely with the many hot spots all over the world.

Promise is one thing the reelection of Jimmy Carter does not offer. The president has campaigned as if he had forgotten nothing and learned nothing. He talks as if he had done well in maintaining national morale, managing the economy and reducing energy dependence. He claims credit for an arms control treaty he cannot pass, and a policy of stopping the spread of nuclear weapons that has backfired.

Worse still, he shows no sign of making any changes. He continues to personalize all issues -- even to the point of citing Army as an adviser in the Cleveland debate. He persists in pitting his secretary of state against his special assistance for national security affairs. He stakes out unrelentingly positions of moral intervention with respect to the rest of the world. He clings to the illusion that retreat in the Persian Gulf and Latin America had no alternative except military action by American troops.

But if improvement is not in the cards for Carter, neither is utter collapse. He has a policy of limiting inflation -- not a brilliant policy, but a better one than Reagan. He has a policy for dealing one than Reagan. He has a policy for the Middle East -- not a brilliant one, but a better one than Reagan.

With Carter, in other words, the country sticks with what is inadequate but not much worse. With Reagan, the country gambles. Maybe conditions will improve. But maybe not. And if not, then what?

My own mind is not made up. I would certainly not recommend either candidate to anybody. My one clear perception is that whatever happens on Election Day, government in this country, and the role of the country in the world, are in for hard times.