Jimmy Carter and Ronald Reagan -- two television actors who are not on strike this season -- started long-running, expensive TV series last weekend as both their "media campaigns" begin on prime time.

The admen who will be hawking these political presidential candidates like breakfast cereal between now and Nov. 4 have chosen dramatically different techniques to present their products. The initial Reagan commercials are low-key "talking heads," as television people call it when the candidate simply speaks into the camera.

The first Carter commercials, on the other hand, are highly dramatized, featuring film clips from the Carter presidency, pictures of rockets blasting off and tanks firing guns, music played by a full orchestra and many other cinematic flourishes.

These different styles reflect both the gambles that the camps take with their $15 million advertising campaigns, and the facts of political advertising on television.

Carter, the unpopular incumbent, is being sold on TV as an intelligent, decent, sensible and energetic president who deserves credit for some worthwhile accomplishments in his first term.

Reagan, the challenger, is selling the notion that life in America could be a lot better than it is and the United States need not be pushed around in the world -- if only he were president.

Reagan's adman is Peter Dailey, a Californian who did Richard M. Nixon's television commercials in 1972. That was a relatively modest $6 million ad compaign, conducted for a candidate who probably didn't need a single commercial to defeat Sen. George McGovern.

Dailey has never worked for Reagan, and is not a member of the candidate's inner circle, but he sounds like many of Reagan's oldest advisers when he describes the former California governor.Essentially, Daily argues, Reagan will win if the voters are properly exposed to him.

"Every time Governor Reagan speaks for Governor Reagan, he does terrific," Dailey said in an interview last week. "He has an enormous ability to generate confidence in himself . . . so we have decided at this point, let's let the governor talk to the American people -- dead on, dead straight, no monkey business."

The Reagan commercials that began last weekend are taken from his acceptance speech at the Republican National Convention in July and from two brief talks on domestic and foreign affairs filmed by Dailey in a room that looks like a library.

The messages in the ads are all familiar. The purpose of the commercials seem to be to make a good impression rather than logical persuasion. For example, near the beginning of the five-minute version of a commercial called "Peace," devoted to national security, Reagan says:

"It's impossible to capture in words the feelings we (he and Nancy Reagan) have about peace in the world, and how desperately we want it for our children and our children's children . . . ."

In these commercials Reagan avoids specifics. "We must take a long, hard look at our present military position" is the way he describes the need he sees for more defense spending.

Dailey's ads end with the voice of actor Robert Stack -- Elliott Ness to several generations of television watchers -- repeating Reagan's campaign slogan: "The time is now for Reagan -- Reagan for president."

Reagan's skill as a performer strengthens these commercials. Dailey is particularly pleased with the "Peace" spot, in which Reagan speaks with great sincerity and intimacy into the camera. Dailey has used film, not videotape, to make the candidate look "softer."

Dailey is less pleased with the five-minute spot on the economy, which has some technical flaws, and in which Reagan appears "a little too strident," in Dailey's opinion. "I want him down," the adman said, meaning quietly sincere, not agreesive. To correct the flaws and prepare some new material, Reagan sat down in front of Dailey's cameras again last week.

Dailey had also filmed some man-in-th-street interviews to introduce Reagan's talking head, but these are being dropped because of adverse reaction to them in the Reagan organization. "They looked staged," Dailey said. The men in the street appeared in a five-minute Reagan ad that ran on ABC television late last month.

It is a cardinal rule in political advertising that a candidate's commercials should reinforce the messages voters receive from "free media" -- that is, the news. As this year's campaign begins, though, there is no easy way for Dailey to apply that rule. As he and other Reagan advisers acknowledge, the recent message from the free media has been that Reagan is off to a rocky start, that he can't quite get his act together.

But Dailey thinks the talking Reagan head is still the best way to start his commercial campaign. "If our strategy was right a couple of weeks ago, it's even more right now," Dailey said in the interview at Reagan's Arlington headquarters.

"I mean," he went on, "not enough people know Governor Reagan, of what he stands for.Not enough people have see him talk. They don't get a chance to see him; all they see are the little clips (on the television news), and the clips they've seen lately have been somewhat controversial. I think we're going to give people a chance to sit and listen to Governor Reagan and get the measure of the man."

If Dailey's initial ad strategy is based on a hunch about how Reagan can make the best first impression, Gerald Rafshoon's commercials for President Carter seem closely tied to more scientific polling information -- specifically, what there is about Jimmy Carter that the public finds appealing.

Judging by the first Carter commercials, the president's pollster, Patrick Caddell, has found a few basic qualities that respondents to his polls continue to admire in the president. They are emphasized repeatedly in Rafshoon's ads. In one spot, for example, an announcer intones:

"President Carter -- the people have come to respect his dedication, his foresight, his stability and his good sense."

Equally important to the initial commercials is their oft-repeated message that Carter is smart and energetic -- two points which Caddell and other pollsters have discovered public doubts about Ronald Reagan. In one Carter ad, for example, while the picture shows the president being presidential the announcer says:

"No matter how many advisers and assistants, a president can never escape the responsibility of truly understanding and ussue himself. That is the only way that a presidential decision can be made and the only way this president has ever made one."

Or, in another commercial: "A president must know as much about an issue as one person can know -- that's his job."

Rafshoon, a little known and modestly successful Atlanta advertising made before Carter's 1976 victory made him famous, has established a formula for these new Carter ads.

Nearly every one -- five-minute commercials as well as 30- and 60-second spots -- combines film footage or videotape of Carter being presidential, one or more messages from the announcer, and testimonials to the president from other politicians, both members of Congress and local officials. The testimonials center mostly on the president's alleged intelligence and energy, and to a lesser extent on his accomplishments.

Rafshoon's spots are briskly paced and entertaining. They are clearly meant to leave the impression that, well, Carter is our president, and he's not too bad at it -- he even does parts of it well -- and the job is awfully complicated, so let's stick with him instead of risking Reagan.

Rafshoon has made a series of five-minutes commercials on Carter as chief of state, as commander in chief and as "planner of the nation's future." That last one, interestingly, reveals no plans for the nation's future, but instead emphasizes how many issues come to the Oval Office, how much information reaches the president, and how good Carter is at mastering it.

Dailey told a reporter last week that he understood Rafshoon had been ready to begin running anti-Reagan commercials, but had withdrawn them. Rafshoon denied this heatedly. "We don't have any negative ads," he said. Adding: "Listen, if we ran negative commercials right now (given Reagan's recent difficulties) it would be redundant."

But Rafshoon did not rule out anti-Reagan ads in the future. And Dailey said that Carter's record provided "fertile ground" for negative advertising later in the fall campaign.