With two dozen days of campaign commercials still to run, the Carter and Reagan camps have settled on significantly different media strategies to try to overcome the fears of genuine swing voters that neither candidate really deserves their votes.

Both advertising campaigns are aimed at a small number of voters who still don't know how they will vote.The Reagan camp is trying to reassure these people that Reagan is competent enough, presidential enough, to deserve their support. The Carter ads respond that Reagan's reassurances are, in effect, phony -- that the Californian is not up to the job, and Carter is.

It seems characteristic of the 1980 campaign that both sides see themselves in the same boat -- a boat whose captain provokes a certain queasiness in a substantial portion of the passengers.

The Reagan camp hopes that a heavy dose of reassurance will prove to be an effective antidote to that queasiness. It is now serving up reassurance on television in two varieties. The first, which every American television viewer has had several opportunities to see already (and will get several more), is a commercial about Reagan's performance as governor.

In a few short moments, with newsreels from those eight years on the screen, the viewer is told that Reagan saved California from bankruptcy, was the greatest tax reformer in the state's history, and improved the quality of life in California so fair-mindedly that even the state director of the AFL-CIO sang his praises. (That same labor official is a staunch Carter supporter this year, but no matter.)

Peter Dailey, the California ad man responsible for Reagan's commercials, is unabashedly proud of this one, and will keep showing it intensively until election day on Nov. 4. "In six weeks," Daily said, invoking the conceptual jargon of the advertising business, "in the span of this campaign, the intensity of this message is nothing, nothing at all." Compared to a serious ad campaign for soap or cereal, in other words, this "documentary" commercial on Reagan as governor won't be shown an unusual number of times.

The second form of reassurance Dailey has chosen is Reagan himself, whom he calls "the greatest political communicator" in recent American history. Reagan appears in almost every commercial, usually speaking directly into the camera, trying to look presidential but not too much like an actor (one of the sources of public queasiness about him). Dailey is certain that to see Reagan is to like him better; he shrugs off criticism of his ads as old-fashioned "talking heads," insisting that people want to feel they know Reagan better, and these ads satisfy that desire.

Dailey has made a new batch of commercials for the last days of the campaign. They are more smoothly produced than some earlier Reagan ads, but they stick to the same message. In the new commercials Reagan himself draws on the impression Dailey hopes the earlier commercials have already left in voters' minds -- that he was a good governor. "We can control inflation," Reagan insists in one of the new commercials. "We did it in California and we can do it for America."

On the stump, Reagan insists repeatedly that "the Carter record" is the main issue of 1980, but the Reagan commercials belie that contention. Dailey had made a few commercials emphasizing how the economy has failed to meet Carter's 1976 campaign promises for it, and his side profits from anti-Carter commercials financed by independent groups, but Dailey's principal objective is to convince swing voters that Reagan can indeed be a president.

The Carter campaign's antidote to voter queasiness about the president draws on another school of political medicine. Classically (Nixon in 1972, Johnson in 1964) an incumbent president exploits his accomplishments in office and those aspects of his record that voters admire. Gerald Rafshoon made commercials intended to take advantage of those traditional benefits of incumbency, but because Carter is an unpopular president without a substantial list of popular achievements, they could not carry the reelection campaign.

Rafshoon, who expresses exasperation at the news media for failing to focus attention on Reagan's past statements and actions, has tried to do so himself. Most of the Carter ads now being shown on network television are challenges to the reassurances being served up by the Reagan campaign.

"A lot of Californians feel pretty good about Ronald Reagan," the mellifluous announcer's voice says in one current Carter commercial, "but others feels a sense of continuing concern." The commercial shows men and women on the street in California talking about Reagan:

A man: "I think it's a big risk to have Reagan as president. Reagan scares me."

Another man: "Reagan scares me."

Another man: "As a governor it really didn't make that much difference, because the state of California doesn't have a foreign policy and the state of California isn't going to be going to war with a foreign nation, and it was just amusing. But as president -- you know, it's scary."

On other commercials the people on the street complain of Reagan's performance as governor: "What he did with the mental hospitals was a crime," "It's already common knowledge that he doubled our tax rate," etc.

Rafshoon has also produced a series of spots showing only an empty Oval Office, with the announcer reading a message like this one:

"When you come right down to it, what kind of person should occupy the Oval Office? Should it be a person who, like Ronald Reagan, has opposed Medicare, and is a strong opponent of national health insurance, and has summed up his position by saying, "There is no health crisis in America?Or should a man sit here who has already put together a workable national health program. . . "

Finally, to revive good feelings about Carter, Rafshoon has produced a series of snazzy and expensive 60-second ads introducing attractive, sympathetic voters who are Carter supporters -- a black schoolteacher in Chicago, a steel worker, an auto worker. Rafshoon's cameras record a slice of these voters' lives while they explain themselves why they're for Carter.