Arnold Schwarzenegger. John Edwards. Grover Cleveland?

It's true. In the annals of illegitimate children born to powerful politicians, President Grover Cleveland must rank uppermost. While Schwarzenegger made it with the maid and John Edwards betrayed his wife with a woman who picked him up in a bar, neither can touch the awful acts of Grover Cleveland.

Cleveland's claim to fame is as the only American president to serve two non-consecutive terms in office, and he's remembered as a courageous and pugnaciously honest statesman. But I've spent three years investigating Grover Cleveland for my new book, A Secret Life, tracing the ways in which Cleveland and his keys aides lied about a sex scandal to save his presidential campaign from the career-ending allegations. It's time to correct the record.

Cleveland's sex scandal was well buried, but I found the long-forgotten affidavit from Maria Halpin, about the violent sexual assault that resulted in the birth of Cleveland's illegitimate child.

On the evening of Dec. 15, 1873, Halpin, an attractive 38-year-old sales clerk working at a department store in Buffalo, New York, was on her way to a friend's birthday party when she ran into Cleveland strolling down Swan Street. Cleveland was a chunky 37-year-old bachelor whose six-foot frame projected a figure of might and vitality. He had been courting Halpin for several months and they exchanged greetings. Cleveland invited her to dinner at the Ocean Dining Hall & Oyster House. He was pretty "persistent" about it, Halpin would later recall.

Their meal together was a pleasant one. Cleveland escorted Halpin back to her room at a downtown boarding house. What happened next, according to Halpin's affidavit, would in another era be classified as date rape. Cleveland sexually assaulted her "[b]y use of force and violence and without my consent," Halpin reported, adding that when she threatened to notify the authorities, Cleveland "told me he was determined to ruin me if it cost him $10,000, if he was hanged by the neck for it. I then and there told him that I never wanted to see him again [and] commanded him to leave my room, which he did."

Six weeks later, Maria became aware that she was pregnant.

The boy was born on September 14, 1874, in a hospital for unwed mothers in Buffalo. He was named Oscar Folsom Cleveland, after Cleveland's best friend (Cleveland would later marry Folsom's daughter despite a 27-year difference in age, and she became America's youngest first lady. But that's another story.)

What happened to Maria Halpin next was a cruel injustice straight out of a Charles Dickens novel. Cleveland arranged to have the child forcibly removed from his mother and placed in the Buffalo Orphan Asylum. Maria Halpin was thrown into the Providence Lunatic Asylum, although the facility's medical director quickly released her after an evaluation, concluding (correctly) that she was not insane and that her incarceration was the result of an abuse of power by political elites.

Cleveland won election as mayor of Buffalo on a clean-government platform in 1881. A year later, he became governor of New York. As "Grover the Good," he won the Democratic nomination for president in 1884. Once he was named to the national ticket, it didn't take long for the media to expose the existence of his illegitimate son. What followed next was a malicious smear campaign: Cleveland's people got the word out that Halpin was a sexual plaything who drank to excess and was intimate with at least three (and possibly four) married men, all of them cronies of Cleveland. Cleveland, it was said, took responsibility for the child's conception because he was the only bachelor among Maria Halpin's gentlemen callers. Cleveland saw the matter through in the most "courageous way," the PR spin went, explaining that his indifference to the boy was due to "doubts about his fatherhood."

Utter nonsense. My research has established that this time-honored version of the Cleveland scandal is fundamentally dishonest—almost entirely a fairy tale. Maria Halpin was no harlot. She was a widow with two young children, a church-going woman held in high esteem by all who knew her. From everything I could discover about her life, she was what in the 19th century would be termed a chaste woman.

Maria Halpin died in 1902 at age 66, with $200 to her name, forever linked to scandal and shame. On her deathbed she reportedly said, "Do not let the funeral be too public. I do not want strangers to come and gaze upon my face. Let everything be very quiet. Let me rest."

I don't know how history will treat John Edwards' ex-mistress, Rielle Hunter, or Arnold Schwarzenegger's maid. But if Maria Halpin's experience is any standard, they'd better brace themselves.

By the way, the next time you're at a cocktail party and somebody asks you who's the biggest lowlife—Arnold Schwarzenegger or John Edwards—you can tell them the worst villain of all was Grover Cleveland.

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Charles Lachman is executive producer of Inside Edition and the author of The Last Lincolns: The Rise & Fall of a Great American Family. His new book, A Secret Life: The Sex, Lies and Scandal of President Grover Cleveland, will be published August 1.