"Washington: Behind Closed Doors" is a delicious hot potato. ABC's 12-hour novel for televsion, premiering tonight, proves more powerful than "All the President's Men" and, because it is likely to be seen by millions more people, could have considerably greater national impact.

In spite of tedious romantic interludes involving the high and the mighty - which ABC insisted be interwoven with the Watergate-inspired political story being told - "Washington" remains, especially in the chapters following tonight's introductory episode, very entertaining and, for TV, very strong stuff.

"Washington" has its slickness and superfliciality, and it is presented as fiction and not documentary drama. But it may bring home the grim reality of political corruption with more immediacy than any previous treatment of Watergate, including news reports. Never before have TV viewers been offered such a concentrated and sustained prime-time dose of bad news about the American political system and the possibilities for abusing it.

The first installment, just over two hours long, airs tonight at 8:30 on Channel 7, The remaining five 2-hour episodes will be seen on succeeding nights at 9 p.m., concluding Sunday.

Unfortunately, the first chapter is probably the weakest, as it sets up the characters and plot elements that will criss-cross and double-cross during the rest of the program. The opener is also the chapter that most resembles the film's source, John Ehrlichman's book "The Company," an extremely uncelebrated first novel by a top Nixon aide now serving a prison sentence for his part in the Watergate cover-up and related offenses.

David Rintels and Enric Bercovici writers and coproducers of "Washington," says that only about 90 minutes of their 12-hour film comes directly from the Ehrlichman book, although they credit him with having "created," as it were, the central character, a power-mad President named Richard Monckton who is surrounded by hatchet men and dirty tricksters.

Obviously a lot of details in the series are pure fiction. A lot of the personal parts had to be made up. But the business lives of the principal players are roughly patterned on men who held these positions during the Nixon administration.

Monckton, superbly played by Jason Robards, is hardly the only recognizable character. Cliff Robertson's CIA chief William Martin in roughly patterned after Richard Helms. Robert Vaughn's Machiavellian Frank Flaherty after H.R. Haldeman. Barry Nelson's genially rumbles Bob Bailey after Herb Klein. Harold Gould's scholarly diplomat after Henry Kissinger. Andy Griffith's crusty President Esker Scott Anderson after Lyndon Baines Johnson. John Houseman's Myron Dunn after John Mitchell. Many other are idenifiable.

At first, especially during the poker portions of the premiere, one may think it would have been preferable to throw out the coy romana clef Ehrlichman games and do a straight names-named factual drams. Or go the other way and fabricate a fantastic "Seven days in May" or "Failsafe" fantasy further from the truth but closer to high melodrama.

But as the story gets going and Robards sinks his teeth and everything else into the Monckton role, it's clear that Rintels and Bercovici made the right choice. They've refrained from a simplistic exercise in finger-pointing and kept enough distance from the actual story to give "Washington" the stature of a tragic fable.

It also frees the actors of the obligation to do impersonations and lets them do characterizations. Only one actor, the writers say, was cast for his physical resemblance to the real person behind the character - Thayer David as FBI chief Elmer Morse, very obviously J. Edgar Hoover.

For Robards, who ironically or not won an Oscar for playing Washington Post Executive Editor Ben Bradlee in "President's Men," the "Washington" show marks several shining hours. His Monckton is not just a portrait in maliciousness but a study in pathos as well. Other characters describe Monckton as "a drab, colorless figure," "a solitary man," "a vengeful man, a vengeful little squirt" and an "anti-intellectual . . . given to the cheap political shot."

The little squirt has dreams of glory. "China - I can recognize her," he says when elected President. "Can you imagine, a lifetime of peace!" Yet he remains viciously determined to deface lingering public esteem for "handsome Billy Curry" (John F. Kennedy), a White House Predecessor, and barks to an aide after making his victory speech, "Let's start picking which of Curry's Ivy League faggots we can throw out on their ass - now!"

This is the creepy climax of the first two hours.

That power corrupts is no big scoop, yet "Washington" reiterates the maim with a fresh and fairly riveting immediacy.We're not accustomed to hearing from network TV that the system can be subverted and made a sham by hooligans; it's not the comforting message TV likes to tell. So when it does break through, even in such fancy dress as this $7.5-million TV blockbuster, it seems all the more emphatic. "Washington" dares to be bitter, and that's sobering.

Subplots involving the sexual capers of the protagonists are much less successful, although Stefanie Powers and Lois Nettleton are basically convincing as CIA chief Martin's mistress and ex-wife, and Meg Foster is movingly vulnerable as Jennie Jamison, one of those unfortunate women who knows she is hooke don a rat. But theirs stories seem like padding and poof compared to the high-stakes grapplings for power, not even Rintels and Bercovici are happy with them.

"We had to put in a little more soap opera than we wanted because there were some people who felt a story as political as this would not have a broad base of support," Rintels says Bercovici.

One finds oneself waiting impatiently for Robards to re-appear. The man is absolutely fascinating to watch, even when he goes so far with Monckton's paranoid tantrums that you expect him to start clicking the steel balls Humphrey Bogart's Capt. Queeg was so fond of in "The Caine Mutiny."

On the other hand. Robertson (incredibly billed above Robards in the opening credits) slogs through another of those comatose performances that threaten to drag other actors down with him. In only one scene is this zombie approach effective - when Robertson's numb exterior is contrasted with the hysterical sobbings of his wife.

Most of the acting is better than average, but Nicholas Pryor as Hank Ferris, who becomes Monckton's press secretary, is a standout, a heartbreaking portrait of panicky sycophancy. Ferris is a small, talentless man who believes all the romantic fantasies about people in power. Being in its presence thrills him; it's its own reward. "The President of the United States knows my name!" he tells his thrilled little wife.

The Washington authenticity; or lack of it, becomes moot once the story starts steamrolling. There are a hundred different versions of most true stories anyway and "Washington" can hide behind its pose of fiction. Do people in power really talk this way? Some dialogue sounds false, but other exchanges bring eerily to mind the halting staccato of the conversation on the White House tapes.

Incidental details of life in the capitol are not consistenly accurate. Georgetown is "a lot like the Village," says one misled New Yorker in the story. The first chapter includes one of those walks we doubt over got walked. Robertson and Powers strat strolling among the presidential monuments and quickly end up at the C and O Canal.

White House staff are supposedly spending an evening at a Washington disco in Part Three, but they're clearly at Dillon's, a club in Westwood, in Los Angeles. A reference to the "nightclubs" of Washington is out of place, since this isn't a nightclub town. With pure mischievousness, the filmmakers set one scene in Part Two inside one of the Watergate Mall shops.

Other Washington locations used include the exterior of the Kennedy Center, the White House, Union Station, and the Lincoln Memorial. The UCLA Confernece Center in Lake Arrowhead, Calif., doubled as Camp David and a Valencia, Calif., college campus became the CIA headquarters in Langley.

Rintels thinks that the show's vision of life in Washington, at least in rooms at the top, is essentially faithful. "We've always felt that we don't want to be the guys who come from Hollywood and give a view of Washington that's an unfair, distorted, 'Hollywood' view," he says. "If we do not succeed in Washington, if people who see the show here think we didn't do justice by their town, then we think we've failed."

There was naturally some network difference regarding this hot topical item. At no time during the entire 12 hours of "Washington" does anyone usr the terms "Republican" or "Democrat." Nor were the writers allowed by network lawyers to use the name "Vietnam," although the war figures heavily in the plot. Instead reference is made to "South-East Asia."

One man, Gary Nelson, directed all 12 hours of "Washington," a TV first ("Roots" had more than one idrector). Nelson had been able to give the production a consistently urgent look, although not even he can do much with the bedroom confrontations.

Also to its credit, "Washington" avoids being a get Nixon festival. Curry's man Martin admits that Curry ordered political assassinations in other countries by the CIA and Martin followed those orders.Martin also disobeys his mandate not to meddle in domestic politics so he can slip anti-Monckton secrets to Monckton's opponent.

And Griffith, in the LBJ-like Anderson role, notes at the end of Part Three, "None of us have lived too clean all the time." This is what Hollywood tells America about Washington in "Behind Closed Doors."