"We're electing a senator, not a commercial," declares the narrator on a commercial for Sen. Alan Cranston (D-Calif.).

But months before Election Day, senators and would-be senators are making a feverish dash to the tube. Gripped with fear that their opponents may set the pace of the campaign, they are racing to put their images on the air earlier and more frequently than ever before.

The incumbent Republicans, who are defending their control of the Senate, have launched many first strikes. By mid-July, 15 of the 19 GOP senators seeking reelection this year were landing before the voters on paid television spots.

The television ads of the 1986 Senate campaign contrast markedly with the intensely focused ads of 1984, when candidates defined themselves by reference to the presidential contest. This year the themes are diffuse. Most candidates stress their personalities and loyalty to their states.

The first ad of the midterm campaign appeared on May 30, 1985 -- 1 1/2 years before Election Day. The commercial featured Sen. Mark Andrews (R-N.D.), who was plagued by low ratings due to rural discontent. "It all began in early May with the biggest rally and fund-raiser in North Dakota," said the narrator. The camera scanned a cheering crowd and zeroed in on Vice President Bush clapping. "It's not too early to go for the best. Go for the A-Team for North Dakota's Mark Andrews," the narrator added.

A few months later, in September, Andrew's neighbor, Sen. James Abdnor (R-S.D.), plagued with a primary challenge he eventually beat off from Gov. William J. Janklow, went on the air. Attempting to make a virtue of Abdnor's perceived colorlessness, an ad showed him sitting in a darkened room, diligently writing at his desk. "He's not like most politicians," according to the voice-over. "He's not loud and flashy."

Another 1985 ad, for Sen. Jeremiah Denton (R-Ala.), explicitly made the case for early campaigning. "It takes some time to get it together," said the narrator, as carpenters hammered together a platform and costumed singers appeared to rehearse syncopated gestures. Soon Denton appears on the completed platform with President Reagan. Almost every sentence in the commercial contained the word "Alabama."

Easily the most expensive and extensive early television campaigning is occurring in California, where Cranston has already spent $1.5 million on commercials and Rep. Edward V.W. Zschau, the Republican challenger, has spent $1.05 million.

Zschau managed to win the Republican primary by spending more than $1 million in the final two weeks of the campaign, most of it on television advertising. His closest rival spent that much in the entire campaign.

"We have been on the air almost continuously since the primary," said Ian Weinschel, Zschau's media consultant. "You have to do it, or you risk taking a slide. It's not only defensive; it's offensive."

"The biggest advantage of going on the air early," said Robert Shrum, Cranston's media consultant, "is that you can define the race. I'd rather have us define the race than the other guy."

Each candidate is trying to present himself as the embodiment of California and the other as anti-California. Zschau is relatively unknown, and Cranston's ads are attempting to fill in the blank before Zschau can. "We'll define him," Shrum said.

Cranston is very well-known: The 72-year-old senator is running for his fourth term. So Zschau (pronounced like "shout" without the "t") is trying to turn Cranston's experience into a liability. According to the Zschau scenario, the fresh face beats the old one.

Zschau's biographical spot begins by making a physical connection between the candidate and the state tree. The tops of towering redwoods are glimpsed from the ground. Then a name in sky-blue letters -- "ZSCHAU" -- falls from the highest branch. It glistens on the screen, as a flash of light swiftly passes from "Z" to "U." This visual effect is accompanied by an aural effect -- a whoosh that correctly pronounces the candidate's name -- a rare instance of onomatopoeia in video campaigning. What follows is a recitation of Zschau's lifetime of relentless upward mobility in school, business and politics. His tagline: "A great senator for California's future." By labeling him a senator, the ad gives stature to the mostly unknown House member. And by identifying Zschau, 46, with the future, the ad implicitly identifies Cranston with the past.

Another ad is more direct. A black-and-white passport-sized picture of an unsmiling Cranston bounces around the screen, like a hapless video game character who finally gets gobbled up. A full-color picture of a smiling Zschau appears. "Ed Zschau lets you know EXACTLY where he stands," reads the legend. Then Zschau, still is full-color, is placed side-by-side with the still black-and-white Cranston. Zschau's positions are listed under his picture, for example: "Taxpayers' best friend." Under Cranston's name, in red ink: "Biggest spender." In a burst of energy, the Zschau picture fills the screen, pushing the small Cranston one into the void. "A great senator for California's future."

"Our positions are California," Weinschel said. "Cranston's are not California."

Unsurprisingly, this equation is reversed in Cranston's ads. In them, Cranston is identified as the image of the Golden State. Striking photographs of the California landscape, taken by Ansel Adams, appear on the screen, as Lloyd Bridges speaks the voice-over: "One great man photographed California. And one great senator is fighting to save it for future generations -- Alan Cranston." An endorsement from the late Adams, who was a Cranston friend, is read: "Alan Cranston is a great leader . . . . "

"People look forward to seeing that ad," Shrum said. "Zschau has bad votes on Superfund and the Clean Water Act. He's a yuppie candidate with a bad environmental record. The ad was partially to set up a favorable on our candidate and the bad side of Zschau."

Another spot attempts to elicit positive feelings about Cranston by comparing him to a pantheon of California favorites: Theodore Roosevelt ("national parks"); Earl Warren ("individual liberty"); Robert F. Kennedy ("stop war"), and, ultimately, Reagan ("Cranston has won more elections in California than . . . . ").

Another spot highlights testimonials from his Senate colleagues, from Edward Kennedy (D-Mass.) to Sam Nunn (D-Ga.), each of whom says something positive about Cranston that the viewer may associate with the man speaking. Sen. Gary Hart (D-Colo.), for example, says, "He's a leader on every new issue we face."

This spot also places Cranston in the context of Democrats other than those on the ticket with him in November, like state Chief Justice Rose Bird, who is extraordinarily unpopular.

So far there are two negative spots about Zschau. In one Cranston ad, blurred pictures of two candidates face each other. "Compare two candidates for the United States Senate," instructs the narrator. "One says, clean up toxic waste. The other voted against tough laws to do it." More opposing stands on various issues are elaborated. "Funny thing is," said the narrator, "both candidates are named Ed Zschau." And the indistinct pictures suddenly come into sharp focus, showing Zschau facing Zschau. Then the tagline: "Cranston, California in the Senate."

Another Cranston spot is a commercial about commercials. A picture of Zschau, framed in a film strip, flickers, as the voice-over warns, "There's a difference between the real candidate and the film." As what it depicts as Zschau's flip-flops are detailed -- "Says he cares about California, but opposed the Clean Water Act" -- his picture flickers and starts spinning.

"Zschau," the ad warns. "Don't be fooled by the film."