He's dashing, he's dedicated, he's patriotic and pure. He's a U.S. senator, appealingly driven and predictably obsessive. He's the man of the moment, looking for love and truth, caught in a quagmire of sinister forces out to destroy his chances of becoming president.

"His life is in shambles," says Sen. Gary Hart (D-Colo.). "He's not very smart politically. He doesn't play the game."

"He's never been on the inside of the club, so to speak," says Sen. William Cohen (R-Maine). "On the one hand, he has pressure being put on him to spend more time with his constituents. And the press is putting pressure on him to run for president."

"He's not pretty," says Hart. "Of all the things he is, he is not pretty."

"Well," says Cohen, "he's a white male. So to that extent, he's like us."

Meet Thomas Chandler, a "moderate" senator from Connecticut and the intriguing protagonist in "The Double Man," a collaboration and first novel by Hart, 48, and Cohen, 44, to be released by William Morrow & Co. this week.

Any resemblances to persons living or dead are coincidental and not intended to start sparks flying in the Senate.

"Pleeeaase," pleads Cohen. "We really did not model him after any one of our colleagues."

Remarkable as it seems, Cohen and Hart have spent nearly five years (in between presidential and senatorial campaigns) quietly penning this intricate spy yarn, filled with plots and subplots, beautiful women and plenty of slimy characters that all lead to the CIA and KGB. There are fathers looking for daughters, fathers-in-law trying to ruin sons-in-law, Cubans and Soviets and Mafiosi, and a deep-seated conspiracy that resurrects John Kennedy's assassination. There's even a spy in the Senate -- a "snake in the tower" -- whose identity is, of course, never revealed.

The plot and prose are fast-moving and well-developed and impressively crafted, particularly considering the level of harmony it takes to produce a double byline. It's all the more fascinating when you consider that political egos are generally the size of the Washington Monument.

"Yes, very big egos" says an executive at William Morrow. "Senator Hart's is a little bigger, of course."

Those close to the project say it was a congenial undertaking but note that there was a certain amount of reconciling of the writing styles to be done. Cohen, a published poet, tends toward the descriptive, while Hart, a published political writer, uses words sparingly.

"Gary thinks a sentence over eight words is too long," says a friend of both. "There was a little bit of a problem with that. Bill would always put in stuff about the purple moon or something, and then Gary would take it out. When Gary was campaigning for president last year, and Bill was working on the book alone, he put back in all the purple moons."

This week, sitting in Hart's Senate office in their matching Navy pin stripes and crisp white shirts, the senators remained polite about their differences. There is a familiarity between them, the kind that comes when two people are veterans of the same war. They are described by staff members as somewhere between "good acquaintances" and "friends."

"It's very hard to convince people that it was fun," says Hart. "The way it truly worked was over time. It took us a long time. We tried to do this thing in a year, and we thought that was a long time . . . In four years, you do have time to reconcile plot, characters, writing styles and all that."

"We got accustomed to each other's way of thinking," said Cohen. "After a while, we were both so familiar with each character that we could write scenes and they would virtually be in an identical style. I would take a section, and Gary would take a section. We would each write a section and swap. We did that over the whole history of the project so the styles became one, they merged."

"It just evolved," says Hart.

"We started out with somewhat different styles," says Cohen. "Gary has a more -- uh -- "

"Austere," offers Hart.

"Yes, austere -- a haiku-like style," says Cohen, in a joking reference to the sparseness of the Japanese verse. They chortle at the witticism. "My style is more baroque," continues Cohen, "and over a period of time I think both of us became -- uh -- "

"We became baroque-haiku," says Hart.

They guffaw loudly, though barely vibrating their pin stripes.

Cohen and Hart are probably more alike than most members of Congress. They are well-manicured, and handsome, and often described as "moderate" politically (just like Tom Chandler). Generally, they are in sync on the social issues and on opposing sides of defense issues. Cohen voted for the MX, for example, and Hart against it.

"I'd say I'm just to the right of the center and Gary is just to the left, so I guess that puts us smack in the middle," says Cohen. "There were no conflict issues when we were writing the book because we stayed away from specific votes. We didn't even give Chandler a party."

They are considered equally ambitious for the White House, although Hart got considerably closer to his goal during the 1984 campaign.

Both are also more literary than the average person.

Cohen has published "Of Sons and Seasons," a collection of poetry, as well as a book about his first year in the Senate called "Roll Call."

Hart has written two books. In 1983, he published "The New Democracy," and in 1973, "Right From the Start," a book chronicling the McGovern campaign, which he managed before being elected to the Senate in 1974. He's a great admirer of Faulkner and quite proud that he can name all the members of the Snopes family.

"The Double Man" was born at 3 a.m. during an all-night filibuster in July 1980.

"We just happened to see each other on the floor of the Senate and decided to get some coffee to stay awake in the dining room," says Cohen. "We started talking about what we would rather be doing if we weren't being senators and Gary said, 'If I were not here in the Senate right now, I'd rather be in Ireland writing a novel.' And I responded that I always wanted to go to Ireland and I always wanted to write a novel."

"So I had a manila folder," says Hart. "And we just flipped it over and started to write the outline. The story just started to spill out."

"In however long it takes to go through a pot of coffee," says Cohen.

"It was at that hour," says Hart, "when Shakespeare says strange things happen."

Cohen came up with the title, which is from a collection of poems by W.H. Auden.

They wrote 80 percent of the book before 1983, most of it in longhand, on planes and in dining rooms, and anywhere else they could catch a solitary hour. And it's all their own words, they insist.

They met quietly every month to exchange chapters and psychoanalyze their characters, with the hopes of keeping the project under wraps until publication.

"We knew that we didn't want it to come out during the campaign," says Kathy Bushkin, Hart's former campaign press aide and now an executive at U.S. News & World Report. "We didn't think it would be right. So when it wasn't finished by early 1983, it was shelved for a while."

But someone, somewhere, found out about the novel, and on the day of the Maine primary, news of it hit.

"But it did not come from the Hart campaign," says Cohen. "It came from another campaign. It was to embarrass him. He was running in the primary in Maine and the suggestion was, 'Can you really believe this guy -- after all, look what he's doing. He's advocating all these new positions and he's writing a novel with a Republican.' They didn't take into account the consequences of such a statement would be very helpful."

Hart, who is interested in running for president in 1988, maintains that he was not embarrassed when news of the book leaked out. This week, however, he did appear more uneasy than Cohen, particularly when the interview turned to questions about the book's romance scenes and his resemblance to the hero (Yale graduate, moody, presidential aspirations).

"No comment," he said, exaggerating a wince, when asked if he was Tom Chandler.

"The Double Man" is about Chandler's attempt to unravel a terrorist plot that is being funded by drug trade in the United States and controlled by a renegade arm of the KGB. His investigation starts to take over his life and eventually causes the collapse of a promising career. He loses girl, job and respectability.

Chandler's romance is with Elaine Dunham, his staff assistant on the investigation. She and Chandler tap-dance around sleeping together for half of the book, and when they do, the description is less than steamy.

" . . . Back at her house, they made love. It was fierce, two rivers of energy rushing together, gloriously, powerfully. No words were needed. Afterward they lay together in bed, listening to the sudden rain tapping against the window, and touching as if they were trying to memorize each other's bodies in the dark."

That's it for the sex.

"We were concerned in the sense that we didn't want it to take away from the story," says Hart. "The story is not a romantic novel. What we wanted to do was handle that part tastefully without detracting from the story."

"We didn't want to use language that was maybe very scintillating but not in good taste," said Cohen. "We wanted to handle it with some delicacy."

They also didn't want to be known as two former elected officials who wrote a sexy book.

"The romance just happened," said Hart. "It just evolved. It wasn't calculated, pro or con."

But a senator sleeping with an aide? Isn't that the stuff scandals are made of?

"It couldn't have been anyone else because he was totally absorbed in the investigation and she was working with him," says Hart. "It had to be somebody he had to relate to. They weren't married."

One of the more revealing aspects of the book is its irreverence for the Senate as an institution, where legislators are described as "too small, too timid, too unimaginative to call for action before calamity struck . . . awe inspired to do so after the fact."

In another memorable description, they capture the silliness of certain legislative measures in the midst of world crisis, in this case in the aftermath of the assassination of the Secretary of State's family.

"He pushed open the center doors of the quietly elegant Chamber of the U.S. Senate, where he must vote for a bill that proclaimed this day -- this day after Friday's carnage -- Seal Day."

"It's not anti-Senate," says Hart. "It's just meant to put things in perspective. Chandler has the right perspective. You live in several worlds in this institution. Chandler is meant to show that you can't go back and forth in those worlds. It's difficult. He gets involved in what he's doing and the more important what he's doing becomes the more irrelevant the sideshows become."

Hart says that, in a way, the book allowed him to release certain impressions he acquired when he first came to the Senate and was placed on the special 1975 Intelligence committee, chaired by the late senator Frank Church, to investigate the CIA, FBI and U.S. and foreign intelligence operations.

"Talk about intense, that was intense in terms of amount of time spent and what you were hearing," he says. "I constantly had to fight through that two-year period with reality. You walked into this hearing room, and all the doors were shut, people chased out, and it was debugged. You hear all this gosh-awful stuff. And then you had to walk out and say hello to the Coloradans. It was an amazing experience. It's the constant shifting of gears, and Chandler tries to keep it in perspective."

And do they think in real life they manage to keep their own perspective in the Senate?

"Better than most," says Cohen. "Oh, you better strike that."

"No, that's okay," comforts Hart, "she'll write 'he said laughing.' "

Hart and Cohen are reluctant to say what lies ahead for Thomas Chandler.

"God knows," says Hart.

"Oh, he's in a big mess," says Cohen.

Which is really a roundabout way of saying that they do not want to discuss the possibility of a sequel.

Or will we be left waiting with that snake in the tower?