Of all the statements President-elect Ronald Reagon made since his election, the most encouraging is that he intends to go all out in getting things done in his first years in power. "I am determined," he says, "to behave as if it's a one-term office."

That's not only good policy, but good politics: nearly all the chief executives we most admire made their mark in their first terms, which in turn virtually guaranteed their reelection.

Most of the achievements that Washington, Jefferson and Jackson are remembered for were first-term efforts. The same can be said of Lincoln and Woodrow Wilson and, of course, of Franklin D. Roosevelt. Harry Truman's first years towered over his later ones, as did Lyndon Johnson's. Even Richard Nixon, despite Watergate, will go down in history as the president who, in his first term, established the opening to China, initiated detente with Russia and negotiated the first arms control treaty.

The first 100 days of FDR's administration, when the foundation of the

The first 100 days of FDR's administration, when the foundation of the New Deal was laid with dazzling speed, ought to be a model for all presidents on how to get things done in the wake of a notable election victory. Back in 1932, the voters rejected Herbert Hoover almost as scornfully as they did Jimmy Carter a few weeks ago. But in rejecting Hoover, the voters did not consciously give Roosevelt a mandate to launch the New Deal. The mandate was a negative one: stop the Hoover depression. Yet that was enough for FDR to start his social and economic revolution.

Today, Reagan is in a somewhat similar situation, in that his mandate, too, is a negative one, signaling no confidence in the Carter administration. But if Reagan acts promptly and imaginatively, he, like FDR, can turn his victory into support for positive action.

While the country is not scared out of its wits, as it was at the depth of the Great Depression, the Nov. 4 election certainly showed the voters want a change, even if they are not sure what it should be. It's a rare opportunity for a new president to get the nation moving again.

Fortunately for Reagan, he will have the unexpected blessing of a Republican Senate, along with an intimidated House that is not likely to offer formidable opposition, at least not at the outset. The president-elect also inherits the most conservative Supreme Court since the Truman days, plus a congenial conservative chairman of the Federal Reserve Board. Thanks to Jimmy Carter, the incoming president will be able to fill most of the top posts in the vast federal bureaucracy with appointees of his own choosing. Before Carter's Civil Service Reform Act, the president had only limited appointive power in that influential sector of the government.

"I think," Reagan says, "that with too many presidents, in fact with most of them, there is a terrible temptation to think in terms of the next election. oThis past administration has been more guilty of that than most."

But, the president-elect adds, "I will not do that." In California, he told Time magazine, "I promised myself that I would make every decision based on the assumption that I would never seek office again." He said that would also be the rule in the White House.

That's a lofty resolution, but it should not be difficult for Reagan to conduct a less political administration than Carter did. All presidents play politics -- sometimes for good reasons -- but Carter never seemed to make a decision without an eye on the polls.

Last year, sensing the public's doubts about him, Carter said that if he could change the Constitution "just by the stroke of a pen," he would limit the presidency to one six-year term. He complained that the public seemed to suspect that there was a purely political motivation behind everything he did. He thought a single six-year term "would be an improvement." But the public disagreed, a Gallup Poll showing 68 percent of the people against the proposal. The common sentiment was: "Too long for a bad president; too short for a good one."

In any case, it is evident that our most esteemed presidents have generally accomplished more in first terms when they had to keep re-election in mind, than in second terms when they were free of that concern. It's cheering to see that this has not escaped Reagan's notice.