When Rick Shenkman was an intern at the House Banking Committee, Richard Nixon broke his heart. The idea that a president could be involved in breaking the law shattered his idealized view of the presidency. But then Watergate pointed him on a quest, provoking Shenkman—now a 44-year-old adjunct lecturer at American University—to think about other presidents and their crimes. Soon, he’d made it his life’s work to analyze the muck swept under the carpet by historians who, in his view, are world-champion sugarcoaters. Having charted the offenses of every president from Washington to Reagan, Shenkman now offers a slap of cold, harsh reality in Presidential Ambition: How the Presidents Gained Power, Kept Power, and Got Things Done, a HarperCollins book being released last week.

Since the Kennedy era, the media have devoted untold hours and dollars to rifling through the closet of each new occupant of the White House. So Shenkman decided to “take investigative reporters’ techniques and apply them backward,” he says. The world, he suggests, needs to know that President Clinton is no more or less ethical than any other president. “They’re all people who are willing to do anything to gain power, to keep power, to wield power,” he says. Circumstances change, he argues—not the men themselves, who are “about the same, with a few bad apples” (like Nixon and James Buchanan).

In these men and their various shenanigans, Shenkman finds a distinct pattern: As society becomes more complex, it becomes increasingly difficult for the president to maintain control. “And every time it becomes more difficult to maintain control,” he says, “the president has to stoop a little lower, morally….It’s reverse progress. It’s slowly getting worse and worse.”

The sainted Thomas Jefferson, for instance, was the very first American president to break a promise, tossing his pledge to reduce the deficit when he deemed the Louisiana Purchase worthy of pushing the nation’s coffers into the red. William Henry Harrison, he says, was the first “to package himself like soap.” James K. Polk established the time-honored presidential tradition of knowingly lying—which he did, by the way, to get us into the Mexican-American War. Ulysses S. Grant tolerated corruption. Grover Cleveland manipulated the press. Long before Kathie Lee Gifford, Teddy Roosevelt pioneered the art of shamelessly exploiting his family for PR purposes. Franklin D. Roosevelt used the IRS to go after his enemies; Dwight Eisenhower sent troops into war zones without congressional approval; Ronald Reagan “manipulated public opinion through elaborately staged events,” says Shenkman.

And Clinton…well, Clinton. He’s not an anomaly, at least according to Shenkman’s theory—he arrived right on time. But as for what the president will be like in 100 years—at this rate—Shenkman demurs with a pained sigh.

“Dear God,” the historian says.—Jake Tapper