There were only 12 presidential contenders on the Kennedy Center's Eisenhower Theater stage last night, but 13 campaigns were going on. The odd man in was Tom Brokaw, running on the NBC News ticket for the post of American Anchor. No dark horse he. More of a show pony, actually.

"America's Future: A Presidential Debate," broadcast live for two hours on NBC, brought all the declared Democratic and Republican candidates together for the first time, but that turned out to be itself a debatable feat. There were so many people on the stage that nobody could discuss any point for very long. What a viewer got essentially was a collection of about three dozen sound bites all strung together. It looks to be a sound-bitten campaign.

In the center of it all was Brokaw, fresh from his rather mediocre performance interviewing Soviet leader Mikhail S. Gorbachev, which aired on NBC Monday. Brokaw stood up and strode about like a hungry young lawyer while the candidates sat before him in what could have been jury boxes or choir lofts. Brokaw proved a very peripatetic ringmaster. He covered more ground than the band leader at a mummers' parade.

In the course of this strutting and fretting across the stage (he resisted any temptation to perform "To be or not to be" from "Hamlet"), Brokaw managed repeatedly to stand between a camera and a candidate, so that director George Paul had to go to another shot. Paul Simon or Richard Gephardt would be talking and then, wham, Brokaw would step right in front of the lens and the candidate would vanish.

Not that the candidates were particularly compelling. Mostly it was the same old stuff -- rhetoric that, after so many roadshow debates, has become tiringly familiar, and here we are almost a year from the election. NBC's debate came across more as a stunt than a public service. It's just a little too early to expect people to care.

Indeed, even the candidates appear to be wearing out. Decrying the Democrats for their "hand wringing" and naysaying about America, George Bush said late in the program, "I'm sorry, I just am all depressed. I want to switch over to see 'Jake and the Fatman' on CBS." What a plug for "Jake and the Fatman"! At any rate, by this time "Jake" was over and CBS was showing "The Law and Harry McGraw."

Although the Bush remark got a big laugh from the crowd, it did present a taste problem, since it grew out of a response to a question about how to deal with the AIDS crisis. Bush said the Democrats were negative about the administration's handling of the crisis, and went from there into a general lament over Democratic complaining about other administration policies.

Back at the Brokaw coronation ceremonies, the Rev. Jesse Jackson got the second-biggest laugh of the evening, after Bush's little viewing guide, when he noted early in the debate that he'd met more "live" world leaders "than anyone here. If you add in the dead ones George Bush has met with, then he outdistances me." Bush has been dispatched several times by the Reagan administration to the funerals of foreign notables.

Bush and Jackson were the standouts last night. Jackson appeared particularly vocal and enthusiastic. Simon, who looked so promising in earlier televised encounters, appears to be losing steam, and he still hasn't come up with a satisfactory explanation for his plan to expand government spending while somehow reducing government spending.

"We can do it," Simon says. "We have the potential to do so much."

Bruce Babbitt, perhaps the least imposing hopeful of either party, and perhaps the least hopeful as well, dared to commit the Fritz Mondale sin when he announced, "It's time to acknowledge that we must raise taxes." It was also time, he said, for the candidates to "stand up" for sound economic policies, and so he stood up. It was a calculated gimmick that wasn't much more than embarrassing.

Still, Babbitt did follow it with a savvy summation of the proceedings. When hardly anyone else would stand up with him, he said, "There aren't a lot of profiles in courage here tonight."

How about a profile in moxie -- Tom (Superboy) Brokaw? Often viewers were treated to what might be called a conductor shot of Brokaw. It was a candidates'-eye view of Brokaw with the vast theater and its rows of spectators behind him, the kind of shot one sees when John Williams is conducting the Boston Pops on PBS. As the candidates' advisers wanted them seen in the most favorable possible light, so NBC was bathing Brokaw in a bold promotional glow.

The broadcast was fat with format. The candidates came out in groups of six for 26 minutes each. They had to answer Brokaw's questions in one minute. Then a man rang a chime to signal them off. This was not "Chimes at Midnight" three hours early. The candidates were playing beat the clock.

In the second half of each 26-minute sequence, Brokaw invited one candidate to question another -- Gephardt questioned Michael Dukakis, Jack Kemp questioned Robert Dole, and so on. Democrats did not get to question Republicans or vice versa.

Explaining this at the outset, Brokaw said the candidates would not only answer questions: "They'll be able to interchange as well."

Generally, the Republicans did more fractious interchangin' than the Democrats, though it was a close call. When the Republicans weren't beating around the bush, they were beating up on Bush. Jack Kemp would not shut up when Dole tried to answer a question about pardoning Iran-contra transgressors. Pete du Pont told Al Haig, "Al, you served in more administrations than I can count." Gosh, it's under five, isn't it?

Among the Democrats, Jackson enjoys a kind of immunity; nobody wants to knock him. Simon, on the other hand, got bopped by Gephardt, who said, "Paul, you're not a pay-as-you-go Democrat; you're a promise-as-you-go Democrat," and observed, "Simonomics is really Reaganomics with a bow tie."

The candidates appeared a little less studied in their television awareness than in the past, but there was a funny moment when Babbitt was supposed to be answering a question from Simon and yet turned away from him and talked into the distance. He was staring into a camera, poor chap, but the camera wasn't turned on. So he just looked rude.

Oddly, Brokaw neglected to leap in front of him once the camera finally did come on.

They talked and talked, and soon a viewer couldn't be blamed for playing the game of who does he remind me of? Albert Gore still strongly resembles Clark Kent, only he never hops into a phone booth to become somebody more interesting. Paul Simon is looking less like Orville Redenbacher and more like Oscar Levant. Al Haig comes across as if he were a larky creation of the late Al Capp.

Pete du Pont is Blake Carrington, but as weird Bruce Dern would portray him. Bruce Babbitt is Jimmy Stewart playing Jimmy Carter. Richard Gephardt blends right into the woodwork, as if he had been colorized but it didn't take. Pat Robertson is as shifty-eyed as ever, oddly avoiding direct contact with the camera. In George Bush there is just a trace -- just a trace, mind you -- of Jack Nicholson. The surliness is inescapable.

And Dole is a tantalizing cross between former NBC newsman Lloyd Dobyns and Hurd Hatfield, who starred in "The Picture of Dorian Gray."

These may be errant, wayward, twisted thoughts -- but they would never have occurred if these candidate debates weren't getting to be a pain in the neck already.

Meanwhile, the Brokaw campaign goes on. It has been a lively week for him. The instant the debate was over, NBC slapped on a Tom Brokaw promo -- a 30-second promo to follow the two-hour promo that had just ended.