Like most marriages, the union between Bill and Hillary Clinton is a mystery, only more so. Is there any other that we know more about yet understand less? How could he do it? Why did she stay?

Now comes the first of the Clinton books to focus exclusively on the relationship. "For Love of Politics: Bill and Hillary Clinton: The White House Years" by Sally Bedell Smith, mines every piece of data from the first "two-for-the- price of one" presidency for the light it sheds on what the second might be like.

Smith puts Hillary Clinton in every frame, and at 572 pages covers everything from the early fumbles like gays in the military to triumphs such as Northern Ireland to the biggest misstep of all, Monica Lewinsky. If she shows Bill lingering on a rope line, or playing a late game of hearts in the solarium, she shows the disciplined Hillary backstage tapping her foot or calling it a night at 10 p.m.

During the first foreign trip, to the Group of Seven meeting in Tokyo, Hillary took her mother along and attended Kabuki theater and a tea ceremony. It wouldn’t be long before she’d keep a separate but nearly equal schedule to her husband’s with her own press corps.

Smith scores coups getting interviews with aides who had ringside seats and had been quiet until now, including former Health and Human Services Secretary Donna Shalala and press secretary Dee Dee Myers.

Shalala warned Hillary not to grab a policy post but recalls the first lady "thought she was part of earning the presidency, and she wasn’t about not to share the opportunity." Thus, we got a health-care diva who produced a 1,300-page bill in secret. This earned her the distrust of lions of the Senate such Daniel Patrick Moynihan, which assured her failure.

Moynihan, who once called for an independent counsel on the Whitewater affair, came around on Hillary long enough to allow her to come to his farm to announce her bid to succeed him in a Senate seat from a state she had only visited as a tourist.

Not so Moynihan’s wife and campaign manager, Liz, who at the outset of Clinton’s unprecedented Senate run, scolded her, "You lie about what happens…You mislead people. You haven’t taken advice."

One of Shalala’s more notable portraits is of a Bible- toting Hillary, who went around Arkansas preaching "What It Means to Be a Methodist," matching the saltiest language of sailors in private.

Once, when Bill had given a speech on Capitol Hill to the National Governors Association where he equivocated on universal health care, she screamed at him on the phone, "What the f– are you doing up there? I want to see you as soon as you get back." Within hours, he was no longer equivocating.

We see the yin and yang of their personalities over welfare reform. Bill considered vetoing the legislation, but Hillary pressured him not to. Hillary "saw the political reality (reform was overwhelmingly popular) without the human dimensions," even though it was her liberal friends who were most opposed to the measure.

These friends included Marian Wright Edelman, for whom Clinton worked at the Children’s Defense Fund, and her husband, Peter Edelman, a high-ranking official in the Department of Health and Human Services, who resigned in protest.

"Bill was anguished," Shalala said. "Hillary was not."

Each Clinton has character flaws that sometimes compensate for, sometimes compound, the other’s deficiencies. Bill’s is sloppy self-indulgence with a bottomless need to be loved, traits captured in George Stephanopoulos’s book "All Too Human."

Hillary makes up for his sloppiness with massive self- discipline that can look all too inhuman when it slips into a desire to control everything and everybody.

In Arkansas, those who knew the Clintons best weren’t surprised by her messy land deal or her killing in cattle futures. She was in charge of the family money, or what she saw as the lack of it, wielding the domestic upper hand with professional and political ramifications lasting to this day.

He was beholden to her almost from the start for not leaving him over his marital infidelities, which would have hurt his (and her) presidential ambitions.

"Clinton, womanizing and sex scandals" appears to consume the most pages. Myers illuminates the attitude that saw Hillary through countless bimbo eruptions, including Monica, which was to behave at damage-control meetings as if she were Bill’s attorney, calling into question "specific things about the story, dates and times," attacking "the motives and the details."

Smith offers up the sad scene of daughter Chelsea reading online the report on the Lewinsky scandal by special prosecutor Kenneth Starr, "which drove her father to tears."

Smith writes that the day after the Starr report came out, the Clintons appeared at an Irish-American dinner where Hillary "put her hand on her husband’s leg" leaning over "and whispering in the president’s ear," prompting Stephanopoulos to observe, "Whatever their private turmoil, Hillary seems signed on for one more comeback."

The Clintons are all about comebacks, this next one, if it happens, the biggest of all. A president dies twice, the first time upon departing the White House with its power and trappings — world leaders a speed dial away, Navy stewards bearing Diet Cokes on a silver tray, intersection control in every city in America. Barbra Streisand croons just for you.

Any pretense that theirs wasn’t a co-presidency and might be again is over. Hillary now speaks consistently in the first person plural as in "we balanced the budget," as if she’d been vice president.

You would think that only in the movies — or Argentina — could a president come back as consort to his wife. If what was unthinkable just a few years ago happens, there’s no better preview of what that would be like than Smith’s book.

Source: Seattle PI