Over the course of his presidential campaign, Donald Trump has been consistent in his inconsistency. Mr. Trump takes both sides of every issue, from Planned Parenthood to immigration to the fight against ISIS, sometimes making contradictory statements just days apart. In fact, the most consistent aspect of Mr. Trump’s campaign has also been its most troubling: a rising tide of anger and violence, tacitly and explicitly incited by Mr. Trump himself. In Chicago on Fri. night and Dayton on Sat. morning, this violence took a sharp and frightening turn.

Trump rallies have increasingly become cauldrons of anger and violence. Over the last several months of the campaign, the Internet has been flooded with countless videos of Trump supporters at rallies ganging up on protesters, shouting them down and physically attacking them. Most of the protesters are nonviolent, guilty only of voicing their sincere opposition to Trump’s campaign. These outbreaks of violence have resulted in several injuries and arrests.

Even more terrifying than the violence itself is the fact that it is inspired, condoned and incited by the Trump campaign and Mr. Trump himself.

In Nov., a black activist was roughed up by Trump supporters at a Birmingham, Ala. rally. The following day in a Fox News interview, Mr. Trump refused to condemn the attack, even suggesting that the protester “should have been roughed up.” In Jan., one protester was dragged out of a rally in Vermont by security, and Trump repeatedly called on security to “take his coat” before throwing him outside in the dead of winter. At another rally in Feb., Trump directed supporters to “knock the crap out of” any protesters they may see, promising that he “will pay any legal fees” for those who do.

These disturbing incidents are escalating both in frequency and severity. Last Tues., Trump supporter John McGraw was arrested and charged for sucker punching a protester who was being escorted out of the rally by security. The following day, McGraw told “Inside Edition” that if he sees the protester again, “we might have to kill him.” Trump still has not condemned McGraw or his actions. Instead, Trump said on Sunday that McGraw “obviously loves the country.” He even said he would would “look into” paying McGraw’s legal fees for the assault, just like he promised.

The violence reached a peak Fri. when a rally in Chicago erupted in fistfights and chaos after it was postponed by the Trump campaign, leading to five arrests and injuries to two police officers.

This trend is clear, startling and grotesque. And let there be no mistaking who is at fault for this tide of violence; Mr. Trump has stoked anger and hatred throughout his campaign for his own personal political gain. Now the country is reaping what Trump has sowed. The violence that is infecting our political discourse is a monster of Trump’s creation.

This is an ugly and seemingly unprecedented development in American politics. The use of violence to intimidate and suppress political opponents has characterized fascist parties in Europe and authoritarian regimes in Latin America, but it has rarely reached the shores of the United States. The closest historical parallel to Trump is the ill-fated Democratic presidential candidate Huey Long in 1935, a man who Franklin Delano Roosevelt called “one of the two most dangerous men in America.” With Trump’s candidacy, the United States’ culture of peaceful political discourse faces a serious threat.

After the outbreak of chaos at Friday’s rally, Trump’s rhetoric was strongly condemned both by Democrats and by his three remaining Republican opponents in the presidential race, all of whom correctly blame his campaign for the swelling culture of anger and violence.

“Donald Trump has created a toxic environment, and the toxic environment has allowed his supporters, and those who sometimes seek confrontation, to come together in violence,” presidential candidate and Ohio governor John Kasich (R) told reporters on Sat. “There is no place for this. There is no place for a national leader to prey on the fears of people who live in our great country.”

“When a candidate urges supporters to engage in physical violence, to punch people in the face, the predictable consequence of that is that it escalates,” presidential candidate and Texas senator Ted Cruz (R) said Fri. after the violence in Chicago, adding: “Today is unlikely to be the last such instance.”

“The great thing about our republic is that we settle all of our differences at the ballot box, not with guns or bayonets or violence,” presidential candidate and Florida senator Marco Rubio (R) said Sat. “And you wonder whether we’re headed in a different direction today. Forget the election for a moment, there is a broader issue in our political culture in this country. This is a frightening, grotesque and disturbing development in American politics.”

During the press conference, Rubio did not have the demeanor of a candidate or even a politician. He did not seem polished or rehearsed, and he was unequivocal with his words. He was candid, reflective and grave. He gave the impression of a man shocked by what the political climate in his country has become.

Later, Rubio was asked if he would support Donald Trump should he become the Republican nominee. Rubio looked down and shook his head in apparent dismay. He answered softly.

“I don’t know,” Rubio said. “I’ve already talked about the fact that I think Hillary Clinton would be terrible for this country, but the fact that you’re even asking that question — I still continue at this moment to support the Republican nominee. But it’s getting harder every day.”

Kasich, Cruz and Rubio are all right to denounce Trump, even if their denouncements have come too late. It used to be difficult for Republicans to take a stand against Trump. Now, it’s morally inexcusable not to. The risks are too high, the consequences too clear. Due in part to complacency from the Republican party throughout much of Trump’s rise, an outcome once considered unthinkable is now virtually inevitable: a dangerous and divisive demagogue is on track to win a major party nomination.

Conservatives may not like Democrats or Hillary Clinton. They may like Donald Trump or parts of his populist message. But anyone who continues to support Trump after this dangerous and inflammatory rhetoric is condoning further violence and demagoguery.

In the wake of this string of events, the Trump campaign and some conservatives have attempted to shift conversation away from Trump’s rhetoric, blaming loud and disruptive protesters for intentionally ginning up anger and tension at the rallies. Even if you grant this portrayal of Trump’s protesters (which you shouldn’t), their being in the wrong does not put Trump in the right.

Strong leaders have no problem denouncing violence among their ranks. They don’t enable it, and certainly don’t encourage it. Any man who gins up anger to further his own power and popularity is unfit for the office of the president of the United States.

It is easy to become desensitized to Trump or to doubt that the implications of his candidacy are so grave. Make no mistake: Trump is the most dangerous man in American politics today. Large numbers of Americans assuming he could never win will only help his chances of doing so.

We should all be concerned about the direction our country’s political climate has taken as a result of Donald Trump’s campaign. Liberals, moderates and conservatives alike must unify in opposition to a demagogue and an inciter of violence and anger. The only way to turn away from the tactics of Donald Trump is to rebuke him decisively through the civil democratic process that his candidacy threatens to undermine.