Kevin M. Kruse and Julian E. Zelizer

Opinion contributors

Democrats are wrestling with how aggressively they will investigate the president and whether impeachment proceedings will ultimately be warranted. Publicly, the discussion has largely centered on worries about the political implications of moving forward. Some Democrats are concerned that aggressive oversight might trigger a backlash from voters; others worry that holding President Donald Trump accountable would only aggravate our already pronounced political polarization.

Democrats shouldn’t think this way. Accountability is essential to the long-term health of our democracy, more important than even healing the nation’s partisan divisions.

The United States learned this lesson 45 years ago. In August 1974, President Richard Nixon resigned from office in disgrace as soon as it became clear that the House would vote to impeach him for obstructing justice in the Watergate scandal and, moreover, that the Senate would likely vote to remove him from office. In a flash, Vice President Gerald Ford assumed the presidency.

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Ford hoped to heal the nation from the trauma of Watergate, telling the country in his first official words as president that “our long national nightmare is over.”

On Sept. 8, 1974, Ford announced to the nation on television that he was issuing a “free, full and absolute pardon” to Nixon for any crimes he might have committed as president. Further legal investigations and prosecutions would paralyze the nation, Ford warned, as “ugly passions would again be roused, our people would again be polarized in their opinions, and the credibility of our free institutions of government would again be challenged at home and abroad.”

Ford’s hopes that he could heal the nation were soon dashed. The president came to be seen as less of a solution than as part of the problem. Some Americans speculated that Ford had been complicit in a “corrupt bargain” with Nixon. A former congressman from Michigan, Ford had only assumed the office of the vice presidency after Spiro Agnew had resigned from it in disgrace over his own scandal in 1973. With news of the pardon, many assumed that Ford’s elevation had been made on the condition that he would pardon Nixon if needed.

America rejected Ford's approach to healing

As a result, Ford found himself the target of a fierce backlash. Ford, who was cheered during an appearance in Philadelphia the days before the pardon, was booed when he arrived at the Greater Pittsburgh Airport the Monday after it. Californian Lee Davis, quoted in The Washington Post at the time, called the pardon “dirty politics.” In Pittsburgh, demonstrators yelled out, “Jail Ford! Jail Ford!” Protesters soon gathered outside the White House holding a banner that read: “Promise Me Pardon and I’ll Make You President.”

Newspaper columnists were brutal as well. “He said he was ‘healing the country,' ” Mary McGrory wrote, “What he was doing was a favor to an old friend while simultaneously trying to sink a nasty situation well before his own re-election campaign.”

Ford’s approval ratings plummeted, from 71 percent after taking office to just 42 percent by the end of 1974. Worse yet, the decision to let Nixon go fueled the distrust of government that had become so pronounced as a result of Watergate and the Vietnam War.

Even Nixon seemed emboldened. When interviewed by David Frost on television a few years later, Nixon defiantly insisted: “Well, when the president does it, that means that it is not illegal.”

The nation has continued to pay for its failure to hold Nixon accountable. The divisions that Ford had hoped to paper over with his pardon have only continued to widen. Moreover, the general trend — toward a vague sense of “healing” instead of holding specific wrongdoers accountable — has only continued to erode the public’s faith in government over the ensuing decades. High-level officials in the Reagan administration clearly subverted the law in the Iran-Contra scandal but escaped any real punishment thanks to pardons from President George H.W. Bush. War crimes committed during the George W. Bush administration, meanwhile, were swept under the rug when the Obama White House refused to insist on accountability there.

A president must be held accountable for crimes

The lessons are clear: If an administration commits crimes without being held accountable, the next commander in chief feels emboldened to keep skirting the rules and violating the public trust. It should not be a total surprise that Trump, who came of age in the decades surrounding the pardon, believes that he can skirt the formal limits of power without having to fear any sort of real blowback.

Turning a blind eye to abuses of power might heal the political careers of individual partisans, but it does nothing to heal the nation. Indeed, a lack of accountability only makes the popular resentment over Washington more pronounced and the partisan divide more deeply felt.

As evidence continues to mount about all that President Trump and his advisers have done to violate the public trust, Democrats won’t have much choice. If they want to heal the nation, not just for what’s happened under Trump but also for what’s happened in the decades before, they should make sure that wrongdoing is set right.

Holding their noses and hoping for the best won’t accomplish anything. Holding those in power accountable for their actions will.

Kevin M. Kruse and Julian E. Zelizer, professors of history at Princeton University, are the authors of "Fault Lines: A History of the United States Since 1974." Follow them on Twitter: @KevinMKruse and @julianzelizer