If you judge by America’s ugly, raucous, invigorating and inspiring political history, it’s clear that the chairwoman of the Democratic National Committee, Debbie Wasserman Schultz, just lost her job for doing it. Politicians are not popes. The leader of the D.N.C. must be a tough pol, more Rahm Emanuel than Barack Obama. Good leaders protect their party’s interest fiercely, as Wasserman Schultz did in opposing a candidate who spent decades boasting of his disdain for her party.

The first formidable D.N.C. chairman, August Belmont, raised the job’s profile after the Civil War by actively soliciting presidential nominees, including Chief Justice Salmon P. Chase in 1868. That effort failed because Chase supported giving black men the vote when most of the party remained racist.

Belmont understood that despite the impressive title, American party leaders often play politics without power. Nationally, presidential and congressional sensibilities dominated. Locally, party bosses like William M. Tweed in the 19th century and Mayor Richard Daley in the 20th wielded far more power than any party chairman ever did.

Today, with primaries empowering party members, not bosses, D.N.C. chairs are supposed to be neutral, but few pull it off. In 1976, Robert Strauss managed it, staying neutral and focusing on unifying Democrats once the surprise nominee, Jimmy Carter, emerged.

Four years later, Strauss’s successor, John C. White, was part of the awkward Democratic convention finale, when he failed to get the insurgent Ted Kennedy to give Jimmy Carter the unity photo he sought. In 1984, Charles Manatt was so evenhanded as chairman that the nominee, Walter Mondale, tried to dump him right before the convention.

More typical was the bias of D.N.C. chairman Paul Kirk Jr., who supported Michael Dukakis in 1988. The insurgent back then, Jesse Jackson, wanted the superdelegates’ votes distributed based on the percentage of primary votes each candidate won. Jackson’s idea undermined the superdelegate’s role as a party-oriented ballast. Kirk defended the superdelegates’ autonomy while professing neutrality in the contest. Kirk’s masquerade was so feeble, that, after Dukakis won the Wisconsin primary, one reporter wrote that Kirk “was careful to say that ‘relief’ was not how he would characterize his own feelings, but he praised Mr. Dukakis’s effort.”

The most successful recent D.N.C. chairmen have been passionate partisans like Ronald Brown and Terry McAuliffe, both big Bill Clinton fans. In 2008, Howard Dean, trying to preserve his grass-roots 50-state strategy, was better at balancing between Hillary Clinton and Barack Obama.

The 19th-century humorist Finley Peter Dunne famously insisted that “politics ain’t beanbag.” No matter how cynical Americans appear to be about politicians, their continuing, immature illusion — politics should be lofty and pure — triggers outrage whenever we (or WikiLeaks) peek behind the curtain and uncover its essential ugliness and roughness.

Let’s stop pretending and welcome the mess. Even the emails speculating about trying to exploit Bernie Sanders’s supposed atheism make sense: Politicians drill down on these perceived weaknesses because many voters care about them. Both parties need leaders who will defend partisan interests vigorously and assess the political environment honestly, as Debbie Wasserman Schultz did, repeatedly. Her successor will make similar moves — or she will fail her party.