Let’s Break a Deal : Divorce: Trump-watchers already are choosing sides in the billion-dollar bust-up of Donald and Ivana. But only time will tell who holds the trump card.

If bumptious billionaire Donald Trump manages to divide his considerable spoils with wife Ivana according to their prenuptial agreement, it will be the deal of his lifetime. But he won’t win without a fight. Because Trump vs. Trump is already sizing up to be the biggest divorce bout of the decade.

The man behind “The Art of the Deal” isn’t shy about touting his phenomenal deal-making ability--make that artistry, by Trump’s measure--which has enabled him to amass a staggering $1.7-billion fortune, according to Forbes magazine. And if the prenuptial agreement should fend off a challenge, the 19th richest man in America will still be in that incredibly rarefied neighborhood. The much-revised agreement, barely two years old, would leave Ivana no more than a relatively paltry $25 million, their 45-room mansion in Greenwich, Conn., and custody of their three children.

But her lawyers are crying fraud and calling the agreement “unconscionable,” a term that packs more punch than ruffled feathers since it’s a court test that could theoretically overturn the pact. They’re saying that as grande dame of major Trump holdings like the Plaza Hotel--a task for which she earned a notorious $1 a year plus all the dresses she could buy--she performed more than the usual wifely duties.

Trump reportedly has branded Ivana an arrogant clone of convicted hotelier Leona Helmsley, and his publicists--super-flacks Howard Rubenstein Associates--supposedly belittled her as little more than a figurehead businesswoman.

Her lawyers are threatening to sue his publicists.

Back to your corners.

Remember Liz and Dick, Jackie and Ari--their counterparts in coupledom, by New York gossip columnist reckoning? Now it’s Ivana and The Donald, as she calls him, and divorce spectators are choosing up their sides of the proverbial aisle, led off by the gossip columnists.

The New York Daily News’ Liz Smith says Ivana walked out: “She still wants to be his wife. But the bottom line is . . . she won’t give up her self-respect to do it. . . . Intimates say she had every chance to continue being Mrs. Trump by allowing her husband to live in an open marriage. . . . “

The New York Post’s Suzy says The Donald walked out: “Get it straight. It’s not Ivana who did the walking out. She wants to stay together at almost any price. . . . It’s Donald who’s breaking it up. . . . “

In fact, this tabloid-nutty town has been virtually papered with giddy headlines about the troubled Trumps. Witness the Daily News’ “Ivana Better Deal” in fist-size type and its peppy “Ivana may bid one no-Trump.” Or the concise “GIMME THE PLAZA,” as the Post blared across its front page.

“It’s got everything but violence,” says Richard Johnson, who edits the Post’s gossipy Page Six.

“Everybody’s fascinated,” says Newsday’s James Revson. “They’ve always been the pivotal glamorous figures. They add a touch of Hollywood to New York.”

If the Trump tussle has captured the attention of even this busy metropolis, remember that New York is also a place where people thrill to any hint of unseemliness in the lives of the city’s impossibly successful people, the gods of commerce and the arts who put the New York in New York.

And that goes double for Donald Trump.

“Just the fact that they’ve flaunted their wealth and their purchases and packaged themselves as this golden-haired royal couple who presided with great lust and fanfare, seeing people knocked down a notch has been catnip to the public, especially New Yorkers who are really tired of the Trump name everywhere,” says professional Trump watcher and Spy magazine co-editor Graydon Carter.

So if the masses are relieved to hear that money can’t buy love, as truisms tell, it can still borrow more than its share of influence, a fact that will doubtless interest Ivana’s lawyer Michael Kennedy, whose mission it is to discredit the prenuptial pact. “There’s not a lot of disagreement (in the marriage), because ultimately Ivana does exactly as I tell her to do,” Donald Trump told Oprah Winfrey in happier days.

Money also comes in handy when it comes to retaining expensive lawyers. Kennedy, once termed “experienced, elegant and deadly” by New York magazine, represented Jean Harris, convicted murderer of Scarsdale diet doctor Herman Tarnower. On Tuesday, Donald retained Stanford Lotwin and Jay Goldberg, whose profile got a boost in the Bess Meyerson trial, for which he represented Meyerson’s companion, Andy Capasso.

Not bad for a mere few days. The public beginning of the end of the Trumps’ 12-year marriage erupted Sunday in Smith’s column, and later reports linked him with model-actress and erstwhile Miss Georgia finalist Marla Maples, who appeared in “Maximum Overdrive” and “The Secret of My Success.” The tabs reported that Maples confronted Ivana in Aspen after Christmas, demanding that the wife surrender The Donald if she didn’t love him. Donald Trump, 43, has repeatedly denied reports of his straying eye. Maples’ spokesman Chuck Jones denied the Aspen incident happened, declining to comment on her relationship with Trump.

But professional gossips for some time have linked him to beauties such as actress Catherine Oxenberg and skater Peggy Fleming, plus fashion designer Carolyne Roehm, married to business tycoon Henry Kravis, and Georgette Mosbacher, cosmetics queen and wife of Secretary of Commerce Robert A. Mosbacher. Smith pooh-poohs rumors about Roehm and Mosbacher, even though Trump has been known to relish reports of his supposed flirtations with the wives of his rivals.

Last year, Trump let it drop to the Daily News that he was being pursued by the former-model wife of Hartz Mountain titan Leonard Stern, touching off a predictable flurry of denials. Trump fanned a few flames himself when he recently fended off a Playboy interviewer’s question about his taste for monogamy. And when Ivana, 40, reportedly went under the knife last year, bobbing a nose and boosting her breasts, speculation was rife that she was mimicking various blonde rivals.

Still, such titillating bits have never really officially advanced beyond speculation until this week. “She’s been protected by the press,” says Smith, who has been hearing such rumors for years. “She’s a nice woman and she’s honest.”

“I periodically get what I consider to be a real tip and I report it out and it would disappear into air,” says Deborah Mitchell, who writes for the New York weekly 7 Days. “I would get denials and all of a sudden, sources who had supposedly seen something firsthand, it became hearsay. It petered out.”

And somehow, with the Trumps’ stronghold onto images that are larger than life, the end of their marriage is being viewed as the symbolic, if belated, end of the decade. “This monied hothouse that New York became in the ‘80s, the Trumps were certainly the exemplars of that value system, and if the ‘80s indeed ended on Dec. 31, this is another cap to that decade,” observes Spy’s Carter.

Of course, the Trumps’ empire, embracing Trump Tower, the Plaza, Trump Castle and Trump airlines, isn’t going anywhere. And there’s nothing--yet--to keep either Trump from walking away with a piggy bank fit for the gods.

Says local gossip Lance of the Hollywood Kids: “He’s got a game show called Trump Card coming out in the fall, and I thought maybe he can have Ivana as his Vanna White, to help pay her off. But definitely, she should get a hundred million.”