Today the major political influences in the country are no longer the Democratic and Republican parties. The major political influences are ABC, CBS and NBC. -- Tony Schwartz, in "Media: The Second God"

WHEN AMERICANS go to the polls today, they will participate in what is essentially just another off-year election. But when they go to their television sets tonight, whoa boy, that's when things start getting Significant. Then the real battle begins.

Yes yes yes, the Republicans probably will keep control of the Senate. But -- will CBS News keep control of the news-viewing nation? A great deal is at stake this year:

* For ABC, election night finds ABC News president Roone Arledge snapping the whip for a three-ringer boasting more newsy superstars than there are in heaven, and featuring the first ABC election night appearance of political veteran David Brinkley, a prestige item who jumped the NBC ship last year after 37 years at 30 Rock.

* For CBS, it will be the first time Dan Rather has anchored an election night since he replaced the seemingly irreplaceable Walter Cronkite in the anchor chair of the "CBS Evening News" in March of '81 -- Cronkite will be on board tonight to interview "important political figures" from Washington, CBS says -- and it will also be the network's first election coverage under the regime of news president Van Gordon Sauter, Mister Moments himself.

* And for NBC, election night will afford much-needed exposure of the new and so far stubbornly unscintillating anchor team of monotonal Tom Brokaw and roguish Roger Mudd, who will be seen side by side for the first time since taking over "NBC Nightly News" last year. The "Nightly News" ratings have stayed pretty much at gutter level ever since.

All three networks are going all-out to outdo one another in reporting election returns and making them appear to be fascinating and in various ways revelatory; they will be taking the nation's temperature so often the nation may get sore lips. Or worse. Each will spend an estimated $2 million to produce tonight's coverage, but the costs zoom as high as $8 million per network when all the pre-election organizational and procedural work is factored in. Each network is outfitted with snappy graphics, snazzy sets and full-tilt computers as part of its election night armaments.

And each network is hauling out its big gunslingers in an effort to attract viewers. ABC News coverage will be anchored by Frank Reynolds, but longtime campaign warhorse Brinkley will be prominently featured. Of course, so will Ted Koppel, Barbara Walters, Sam Donaldson, Sander Vanocur, Richard Threlkeld, commentator George F. Will, and considerably more than a host of others. The ABC roster has been so overloaded that there is reason to wonder if anybody will get to say much of anything, and insiders say Brinkley is privately miffed about the overkill. As the anchor of "This Week With David Brinkley," he's been relatively sheltered from Arledge's flame-thrower approach. This is his first real taste of rampant Roonerism.

However, Brinkley himself said yesterday, "There's nothing to that." Asked if the hyperactive Arledge had overcrowded the runways, Brinkley said, "No. There are a lot of people here, but most of them won't be on until 11 or 12 o'clock." He, Reynolds and Koppel will be giving returns until then, Brinkley said.

"If you're going to cover something, you might as well cover it as best you can," says Arledge, meanwhile, from his New York office. "In our opinion, we have built the strongest lineup of correspondents of any of the networks . . . I think it is the best lineup of correspondents that any network has ever put on election coverage." Arledge says he's only sorry he couldn't find something for Peter Jennings and Pierre Salinger to do. He doesn't mention Geraldo Rivera.

Frank Reynolds is a competent anchor, but Brinkley is an Eminence. Were there any ego or billing problems involved in moving Brinkley onto Reynolds' turf? Arledge says not. "Frank Reynolds will put us on the air, but David Brinkley is David Brinkley. In terms of who's going to say 'Good evening' and 'Good night,' it's Frank Reynolds. Frank is the main anchor."

But Arledge obviously intends to flaunt Brinkley, the toniest Roman he has ever lured to his network. "If you're going to spend five hours with somebody, David Brinkley is the person to spend it with," Arledge says. "Even more than Walter Cronkite , in a sense, David is identified with elections. And I think the reason is, people feel comfortable with him." Arledge says Brinkley is particularly useful in early hours of election coverage "when not much is happening."

Arledge is certainly sitting pretty when compared with the news departments at the other two networks. The morale at CBS News right now is a shambles, insiders say, particularly as staff members in the esteemed, Murrow-founded CBS Reports unit wait for a budgetary axe to fall. Sauter has not exactly triumphed in the way he handled the controversy over the CBS News broadcast "The Uncounted Enemy: A Vietnam Deception." (An in-house report on the broadcast, which was not to be made public, will be made public this week, sources indicated last week, because if CBS doesn't release it, lawyers for Gen. William C. Westmoreland, who has filed a $120 million lawsuit against the network, will.) In addition, the faltering and stumbling "CBS Morning News" is a disaster, and Sauter personally engineered much of its overhaul.

But Sauter sounds, as always, buoyant and blustery, as when he denies that a lot of the reputation and luster of CBS News is riding on whether or not, as is traditional, CBS beats the other guys tonight in the ratings. A showdown? "We have not perceived it that way," Sauter says. "We have not perceived it as the beginning of a scorched earth policy of any kind. It's an election night. I don't know a single person who views this as a momentous symbolic occasion.

"I don't think there's a big ego involvement in it at this stage. Obviously, you'd like to be No. 1. But you concentrate on doing the best you can."

Arledge and his superstars could conceivably not only elbow NBC News out of second place, but elbow CBS out of first this year. But asked if he expects to win, Arledge says, "I don't know. I doubt it. I really don't know. I don't think it means what it used to mean when CBS and NBC fought like heavyweights over it."

How these guys love to deny they're maniacally competitive!

In terms of the news year, tonight's coverage would appear to be the Super Bowl for network news. Reuven Frank, president of NBC News, says he thinks of election night as largely an exercise "by journalists for journalists" and adds, "We're telling ourselves and each other that it's the Super Bowl. But that great big audience out there -- they decide, not us." And if precedent be any guide, that great big audience out there will turn in enormous numbers not to election coverage on any of the networks but to splashy movies and other specialty numbers programmed by enterprising local stations. The silent majority speaks.

And what a pity, considering all the trouble the networks go to. CBS News has thoughtfully supplied a statistical fact sheet on its coverage that indicates just how much trouble it is, and to tell us what we really want to know: how much lumber and "dove-grey paint" went into the big studio set (15 tons, 30 gallons) and how many office supplies were ordered (76 dozen pens, 1,000 pencils, 5,000 sets of "multi-copy paper," 10,000 index cards, 150 ashtrays, 125 wastebaskets and so on).

Over at NBC News, no ashtray count is yet available. But the network has sprung for a huge new electronic scoreboard that will flash out election results in the same splashy style as that famous animated billboard on Times Square in New York. Asked how much mazuma was splurged on this gizmo, NBC's Frank says, "We borrowed it. We give it back Wednesday." Over at ABC, Arledge huffs, "We tried that in 1980, but I thought it looked too glitzy, so I made them take it down." And this from the Guru of Glitz!

For Frank and NBC News, election night is especially crucial. It could help establish in the public mind the concept of Tom Brokaw and Roger Mudd, coanchors of "NBC Nightly News," as a true team, the way the conventions of 1956 established Chet Huntley and David Brinkley.

"For us, it's kind of important in that Mudd and Brokaw will be seen physically together for the first time, and that could be very good," says Frank. "They're on the air together every night, but you never see them in the same shot, because Brokaw's in New York and Mudd's in Washington. Part of making this thing work is how people perceive them together.

"Huntley and Brinkley were never together physically, either -- except maybe once in 10 years, the day Khrushchev came to New York. But after people saw them together at the conventions, they were a pair. That perception carries over, and people think of them differently, and that's important."

Those who follow the coverage will be witnessing a true slugfest. ABC's Arledge is pouring on the hype in the hope of looking not only successful but respectable (Roone will now sing two choruses of "The Impossible Dream"). Sauter can be expected to turn the pizazz machine all the way up as well; he's a scrapper. But if ABC News has its Barnum in Arledge, and CBS News its Bailey in Sauter, NBC's Frank -- who has more election coverage experience than both of them -- remains odd man out. He's often called a class act, but it's no act. Frank thinks about the new arsenal of election night coverage -- computers, exit polls, an endless stream of data on What It All Means--and sighs, at least a little, for the old days.

"Technology is a juggernaut, and whoever stands in the way gets crushed," he says. "I'll tell you what the computer does. It gives you, on election night, the material you really want to read in your Sunday paper after the elections are over. Now you're denied that. They've already told you how the wide-eyed Icelanders in the states of the upper middle west voted, and why. The Sunday paper now is full of what's going to happen next year.

"And," says Frank, "I don't believe that stuff, anyway."

Frank can remember a year when some enterprising producer at NBC News, in the never-ending quest to make election returns more exciting for viewers, proposed making the perennial "horse-race" analogy literal -- rigging up a big display with cardboard horses and jockeys for viewers to watch. The idea died on the drawing board, but it'll be a horse race tonight just the same, and the horses are named ABC, CBS and NBC.

From a CBS promo: This is Dan Rather inviting you to join us for CBS News election night coverage. With so much at stake, you can't afford to miss it.