In every campaign, some political partisans believe their chosen candidate is exalted, while opponents are worthless.

A woman walks past an anti-Hillary Clinton ad near the Republican National Convention in Cleveland, Ohio, July 20, 2016. REUTERS/Shannon Stapleton

This year, however, more partisans are deriding opponents as downright criminal.

This approach to political warfare, once confined to the conspiracy fringe, is bad for American politics and dangerous for the rule of law.

The problem began with a few strident Republicans targeting former Secretary of State Hillary Clinton. But the conventions are revealing it’s infected broad swaths of the GOP — and even a few diehards in the Bernie Sanders movement.

Top Republicans spent months obsessively dreaming that Clinton would be indicted for mishandling classified emails. That the Republican FBI director handed down no indictments when he recently closed that investigation seems to have only heightened the partisan ardor.

That was apparent at the GOP convention, where speakers cast Clinton as more of a criminal than a candidate. And delegates picked up the cues.

Indeed, the party’s delegates chanted “lock her up” so often, Politico reported the phrase was the convention’s “unofficial slogan.”

New Jersey Governor Chris Christie, a former prosecutor, led the hall in a call and response chant to establish Clinton was “guilty” of various infractions. The audience yelled out her guilt seven separate times.

Christie leads Republican presidential nominee Donald Trump’s transition team and is widely rumored as a favorite to become his attorney general. How could Christie credibly oversee investigations into the opposing party, however, after goading his base into that abbreviated political trial?

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It’s a question senators might ask at his confirmation — and one some conservatives are already posing.

Reflecting on the “frenzied response” to Christie’s “call-and-response,” Fox News analyst Charles Krauthammer said the spectacle was a reminder of “why trials are conducted in a courtroom and not a coliseum.”

Not to be outdone, former New York Mayor Rudy Giuliani, another veteran federal prosecutor, said in a speech Friday that Clinton was a “crook” and a “criminal.” He was not simply using hyperbolic political rhetoric, which became evident as he meticulously, ominously explained how to reopen the case against her when Republicans win the presidency in November.

“If Donald Trump becomes president,” Giuliani said, “the statute of limitations will not have run. We can reopen the case, so she’s going to be running to try to prevent getting an orange jumpsuit.”

Giuliani knows that FBI Director James Comey, who is also a former Republican U.S. attorney for New York, investigated Clinton’s email and closed the case after finding no evidence of criminal wrongdoing.

The notion of reopening a closed case because a new party is in office runs counter to the foundations of America’s nonpartisan legal system. It’s exactly why the FBI director has a fixed 10-year term, regardless of who wins the election. In the United States, what is illegal is not supposed to change depending on who is in power.

It’s not just political surrogates and attention-seekers pounding this theme, either.

Back in July, Trump himself said if Clinton was not indicted, the “five year statute of limitations” would not have run when he enters the White House, and “I’m sure the attorney general will take a very good look at it, from a fair standpoint.”

The prospect of politicians using investigations and prosecutions to settle political scores is a problem Americans generally associate with foreign failed states, not the unabashed promises of a major party.

As former McCain strategist Steve Schmidt put it during the Republican National Convention, many Americans may see these kind of threats as too “Banana Republican.”

That may be true. Yet the “political risk” of this tactic ought to be beside the point. Weaponizing the U.S. justice system is irresponsible governance, and any politician aiming to investigate or jail opponents, based on their views, is violating the law.

In the current moment, that fairly obvious line is apparently become harder for many to see. It is a selection of top Republican officials who led this effort against Clinton, despite the FBI’s nonpartisan findings, and they bear the most responsibility. It is also worth noting these leaders are not alone.

When polled after the FBI announcement, 90 percent of Republican voters said they disagreed with the decision. That is a remarkably reflexive urge to equate the opposition with criminality.

And Democrats are not immune. As their convention began on Monday, some delegates and supporters of Senator Bernie Sanders of Vermont marched through Philadelphia chanting “lock her up!” Others hawked “Hillary for Prison” shirts.

While the sentiment was far harder to find than at the GOP convention, it still marks a disturbing migration of the tactic.

This kind of fact-free political vengeance is not normal, even if it’s being normalized.