A year from now, if Ronald Reagan is elected president, the federal government will be substantially run by people like David Gergen.

You're probably never heard of Gergen. He's a promising young Republican-around-Washington. He is 38 years old. He was director of communications in the Nixon and Ford White House. Now he's managing editor of Public Opinion, a magazine published by a prominent Republican think tank called the American Enterprise Institute.

He is part of a new phenomenon in Washington -- the Republican government-in-waiting.

This is not to say that it's all set for Gergen to join the government. For one thing, he endorsed George Bush for president. For another, he likes his present job fine.

Nor is it considered good form for people to admit to a burning ambition to serve in the high appointive ranks of government. "Let's face the facts," says Gergen. "You're not going to find anybody who says I'm dying to get in the administration. First, it's gauche. Second, people are genuinely undecided."

But the fact remains that Washington is full of people who are thinking about the possibility of serving in a Reagan administration, and subtly maneuvering to make that at least a possibility. If Reagan wins, Gergen himself may or may not serve, but lots of people he knows will.

What's noteworthy about these prople is that they're Republicans. It's not unusual for new Democratic administration to fill their ranks with people from foundations, research groups, law firms, and universities on The East Coast. Jimmy Carter did just that, his promises of a government filled with outsiders notwithstanding.

In the eleven years since the last time a Republican took over the government from a Democrat, a similar network of institutions on the Republican side has grown and flourished to the point where its imprint can be clearly seen on the lists of advisers to Reagan.

The Republican government-in-waiting is not monolithic -- in fact, it is divided into several factions. It is not yet completely identified with Reagan, though it's getting there. But it is clearly in place and ready to take power in a Republican Washington.

It central institutions are the American Enterprise Institute, where Gergen works, Georgetown University's Center for Strategic and International Studies, and the Heritage Foundation (all in Washington), and the Hoover Insititution on War, Revolution and Peace at Stanford University in California. All are well-respected, well-financed by corporations and foundations, and growing rapidy. AEI, the biggesst, has grown tenfold over the last decade.

They are symbols of a recent drift to the right in the country's intellectual climate, and of big business' increasing commitment to the battle for the hearts and minds of the government and the public.

The people connected with these institutions are for the most part not the kind of feisty, western free enterprisers that Reagan talks about in his speeches. Indeed, most of them probably would have preferred to serve in a Ford, Bush, or Baker administration, and are now engineering the transition from first choices to Reagan.

Most of them live on the East Coast amd more of them live in Washington than anywhere else. They are not small businessmen, unless you count the consulting business. Their lives have not been spent meeting a payroll.

Ideologically, they stretch across the spectrum of American conservation, from the "New Right" to traditional Republicans to "neconservative" Democrats. Reagan himself has carefully avoided taking sides in their squabbles.

But he does seem to be, in the nice phrase of old-fashioned Southern politics, "getting right" with the government-in-waiting.

Reagan's chief foreign policy adviser, Richard V. Allen, is an old Washington hand who served in the Nixon administration and has put together a list of Reagan advisers that is full of such familiar names as Alan Greenspan, Caspar Weinberger, and Donald Rumsfeld, representatives of all the above-named think tanks, and very few early Reagan supporters.

Allen even had breakfast at the Sherton-Carlton hotel last week with Henry Kissinger, a man toward whom he is well known to feel unfondly (Allen once worked for Kissinger; it ended badly with Allen out of job.) and who Reagan has repeatedly made a point of criticizing.

"We see the world approximately the same way," says Allen. "I am impressed that as never before there is a consensus in foreign affairs in the Republican Party."

For their part, the people on Reagan's lists of advisers describe him with Washington code words of approval: cautions, responsible, nonideological. Asked who they think would serve in a Reagan cabinet or White Housestaff, they name their acquaintances.

So the idea of Reagan ad a radically conservative populist galloping out of the West stems to be fading, in Washington if not among the voting public. "We don't want to dismantle the government," says one of Reagan's top advisers. "We want to improve its efficiency. We want a well-managed conservative welfare state. And Reagan is not Goldwater. He is not a mad ideologue."

What he is, if not that, is not clear, nor is it clear what parts of the government-in-waiting he would most closely embrace.

The traditional Republican wing, whose spirtiual home is AEI, has the problem of having initially supported Republicans other than Reagan. But its members populate Reagan's adviser list fairly densely -- people like lobbyist Charls Walker, initially for Connally, former treasury secretary George Shultz, and Fred C. Ikle, former director of the Arms Control and Disarmament Agency.

This group is conservative in its instinctive mistrust of mass politics and of radical change. Its main priorities for the government would be continued increases in defense spending and limits on overall federal spending. cIts members want to balance the budget, and to encourage capital formation.

They are making the transition to Reagan smoothly. As Ray Cline, a former deputy director of the CIA and a George Bush supporter, puts it, "I have said when George Bush drops out I'd be perfectly happy to advise and consult with Reagan. It's very important to join in and support him, not to allow him to become the candidate of the conservative wing."

The conservative wing of the party has only one member on Reagan's 12-man "policy council," Rep. Jack F. Kemp (R-N.Y.). "Personally, I tend to doubt that the New Right will have a part in the Reagan administration," says Paul Weyrich, director of the Committee for the Survival of a Free Congress, a leading right-wing political organization. "We tend to be very controversial."

The New Right is difficult to define precisely, but its members include buccaneering businessmen (like Joseph Coors, founder of the Heritage Foundation), foundamentalist Christians, and the kind of smalltown and rural conservatives who keenly feel each intrusion of the federal government in their lives. Unlike mainstream Republicanism, it is frankly anti-establishment and in favor of radical change.

Issues like abortion, pornography, and the Equal Rights Amendment have great force on the New Right, and so does cutting taxes. Reagan has often spoken in favor of a 30 percent tax cut, an idea that the traditional Republican government-in-waiting doesn't think much of and has been trying to downplay.

Last month Jude Wanniski, the chief propagandist for the 30 percent tax cut over three years, gave an interview to the Village Voice that was dramatically headlined, "The Battle For Reagan's Mind," that set the mainstream government-in-waiting's teeth on edge.

"Wanniski is a self-promoter who has used his second-hand access to Governor Reagan to toot his own horn," says one Reagan adviser. "The governor found his Village Voice interview appalling. He doesn't have that influence."

The third group with hopes of influence and jobs in a Reagan administration is the neoconservatives, several of whon -- Irving Kristol, Aaron Wildavsky, and Jeane Kirkpatrick, for instance, all professors with ties to AEI -- are on Reagan's list of advisers. However, they have one problem: most of them are registered Democrats.

The neoconservatives strongly supported Hubert H. Humphrey in 1968, strongly opposed George McGovern in 1972, and now identify most strongly with leaders like Sen. Henry M. Jackson (D-Wash.), Daniel Patrick Moynihan (D-N.Y.), and AFL-CIO president Lane Kirkland. They are animated mainly by a hatred of the Soviet Union and what they see as the "anti-Americansim" of the Democratic liberals.

Thus, they are slightly uncomfortable with the New Right, with its emphasis on Christianity, its hostility to the East Coast, and its hatred of organized labor and the welfare state. "Those people are different from us," says one neoconservative. "They believe communism comes to power beginning with OSHA. They believe the Soviet Union is one giant OSHA with nuclear weapons," says this person of the Occupational Safety and Health Administration.

But in January, a group of prominent neoconservatives had a meeting at the White House with President Carter and several other officials.

According to people present at the meeting, it began with a brief statement by one of the visitors, Austin Ranney, a political scientist affiliated with AEI.

Ranney reportedly said that there were two prevailing views of the Soviet Union: that it was a mature superpower that could be dealt with in good faith, and that it was dangerous, expansionist, and fundamentally hostile to the United States.

Carter had held the first view for most of his term, Ranney said, but the crises in Iran and Afghanistan seemed to have made him change his mind -- a change the visitors supported and applauded.

Carter reportedly answered by saying that Ranney was mistaken, that his policies had not changed, that they had always been based on a consistent view of the Soviet Union. "It was a very unsatisfactory meeting," says one participant.

In the meantime, Reagan was courting the neoconservatives -- writing them meeting with them recruiting them for his advisory committees through Richard Allen.

"We are really treated quite badly by the Democratic Party," says Jeane Kirkpatrick, "and meanwhile we are bombarded with friendly messages from Republicans. After a certain time it begins to seem irresistible, especially if the person seems very likely to be the next president of the United States."

A symbol of the rapprochement between Reagan and the neoconservatives was a symposium held at a Washington hotel last month.

In considering the symposium, as in all exercises in Kremlinology, the subject (Russia and American thought) is less important than who was sitting on the dais.

The sponsors, among others were the Coalition for a Democratic Majority, chief political organ of the Henry Jackson wing of the Democratic Party, and the republican Study Committee. The major participants included such prominent neoconservative Democrats as Ben Wattenberg and Norman Podhoretz, the ubiquitous Richard V. Allen, and nobody from the White House.

Jobs with Reagan were not discussed, but then, at this stage of a government-in-waiting they never are.