When a West Coast reporter complained recently to Ronald Reagan's campaign manager, John P. Sears III, that Reagan had not said anything new in months, Sears smiled and shot back, "I certainly hope he hasn't."

And when the 68-year-old Reagan was asked a few nights later what he would do to disabuse voters of the notion that he is too old to be president, Reagan quipped, "Skip rope through the neighborhood."

These statements epitomize the take-it-easy, say nothing strategy Reagan has followed with few deviations since he formed his fund-raising 'exploratory committee" eight months ago. Enjoying his favored status as Republican presidential frontrunner, Reagan has been content to stay on the sidelines through most of 1979.

Now, however, the script is about to change.

Tuesday night, before a Republican fund-raising dinner at the New York Hilton Hotel, the former California governor officially will unfurl his candidacy and then embark on a five-day, nine-state tour in which he has promised to discss issues and answer what sears expects will be "sharp and challenging" questions by the press.

Because Reagan has said so little for so long, and because the new speech will be televised to much of the nation Tuesday night, his managers see the Reagan launching as a pivotal event.

With the spotlight on him, a man who would turn 70 within a month of his inauguration as president will seek to demonstrate that he is an appropriate candidate for the 1980s. He must also, in Sears' words, "get people to look up a little bit" while showing that he has the vitality, ideas and capacity to serve as president of the United States.

"When the central question is leadership," says Sears, "the candidate must be perceived as someone who can solve the problems."

This means, in Sears' view, a speech that shows Reagan is neither too old nor too old hat. It would be a difficult manuever because Reagan also is trying to remind the faithful supporters who have been with him since his "island of freedom" speech for Barry Goldwater in 1964 that he is not abandoning principles to capture an ill-defined center.

"There wouldn't be any point in even considering this race if I were willing to change what I believe in order to garner a vote here and there," Reagan said recently.

Nonetheless, the Tuesday speech is designed to present another Reagan, if not a new one, a Reagan who is supposed to offer both fresh ideas and new leadership.

Sears believes that the Democratic Party, "the major political institution that's been running the country for the past 50 years has run out of ideas." If the GOP can capitalize on this, he adds, it will start winning elections it has been losing.

Reagan may find it easier to solve the ideological equation than to answer questions about age or fitness. As an eight-year governor of the nations's most populous and diverse state, he compiled a record more moderate than his national rhetoric suggests.

A survey taken when Reagan left office found him highly popular with moderate Republicans and with many Democrats.

Sears further suggests that many of Reagan's positions on both economic and national defense issues are more popular now than they were when Reagan first took them.

Whenever Reagan is trying to convence the voters of anything, he turns to television -- and this will be his principal reliance this week.

On monday afternoon he will tape the same half-hour speech he will give to the GOP fund-raiser the following night. It will be seen Tuesday night in three-fourths of the nation's television markets at a production and distribution cost of more than $400,000. The Reagan campaign put together its independent network after the major networks refused to sell the time.

Sears, who played an important management role in Richard M. Nixon's successful 1968 presidential campaign and almost pulled off a Reagan upset of President Ford in the 1976 primaries, is not leaving the perceptions of Reagan to chance.

As Reagan tours the Northeast and Midwest next week, Sears will unveil endorsements from moderate GOP leadrs designed to convince skeptics that a Republican bandwagon is forming behind Reagan.

"We should take advantage of being a frontrunner," Sears said in an interview Friday. "others don't have that luxury."

Sears' comments are studded with references to other frontrunners who tried to sit on their supposed leads -- notably Republican George Romney in 1968 and Democrat Edmund S. Muskie in 1972 -- and he does not intend to have Reagan repeat their mistakes.

"You have the problem, especially if you're the frontrunner, of maintaining the discipline to say precisely what you mean," Sears said. "You can't let down. If you're off by one hair, it will cause problems. I'm not worried that reagan will make a fatal error but even if you make a small error, the time spent going back on it will be a hindrance."

Reagan has made his share of mistakes in two previous campaigns for the presidency and two races for governor of california. But he is, on the whole, a polished campaigner who holds his own in interviews, especially on television.

While some have suggested the Sears strategy for 1980 resembles Nixon's campaign of 1968, sears insists that is not fair.

"To say that Nixon in 1968 was controlled is mild," says Sears. "He didn't make any news and he declared moratoria on a number of issues. We're not in that position. We expect to make news.

"It wouldn't be good to try to hide," he added.

Reagan's schedule next week is demanding. After his Tuesday night speech in New York, he flies to Washington around midnight. He plans a press conference at 10 a.m. the next day in the Senate's Dirksen Office Building.

Then he plans to depart for rallies in Boston and Manchester, n.h., returning to New York the same night. Before the week is out and he returns to his home base in Los Angeles, Reagan will have visited Philadelphia, Chicago, Milwaukee, Grand Rapids, Mich., Atlanta and the Florida GOP presidential preference convention in Orlando.

In his California campaign, Reagan was known as a candidate who could endure a grueling schedule for a short time, as long as it was followed by a period of rest. Those who know Reagan say this may be a byproduct of his work schedules in the movie business and its common pattern of intense periods of hard work followed by long spells of inactivity.

After his first week of campaigning, Reagan is scheduled to take a week off and then hit the trail again for five days in a cross-continent schedule that includes stops in Alaska, Minnesota, Arkansas and Alabama. He plans light campaigning in December including a probable stop in Iowa, and then heavier, more constant campaigning after the first of the year.