Last week, we saw an uglier side of the U.S. political system. An angry mob took to the streets of San Jose, California, to protest presumptive Republican presidential nominee Donald Trump. As it so often does in the California Bay Area’s politically charged environment, things got out of hand. Protesters hurled eggs, threw punches and generally intimidated Trump rally-goers.

San Jose is just the latest example of the grand tradition of left-of-center activism getting out of hand. There is a long history dating back to the late 1960s of the “peaceful” left becoming overly rowdy. The Detroit and Newark riots in the summer of 1967 and the violence at the 1968 Democratic National Convention in Chicago are just a few examples. In 1992 there were the Rodney King riots. More recently violent protestors took to the streets following accusations of local police brutality in Ferguson, Missouri, and Baltimore, Maryland.

All of those examples led to a heightened law enforcement presence, including the deployment of the National Guard, and are a stain on American history.

When in U.S. history has there ever been a right-of-center political protest that has gotten out of hand and led to the deployment of the National Guard?

One might argue that the runup to the Revolutionary War against British taxation and the anti-tax Whiskey Rebellion in 1791 were somehow conservative, in a modern understanding of the label. But if you look throughout history, it’s hard to make the case that any sort of political protest on the right end of the political spectrum led to significant violence.

Some might say the Civil War is an example, but you can’t make the argument that war initiated to preserve the system of slavery — the ultimate restriction of personal liberty — is a conservative cause.

Fast-forward to 2016. If you Google “Republican riots,” one of the top search results is the 2000 “Brooks Brothers riots,” which was a protest at a ballot recount meeting of the Miami-Dade County, Florida, election canvassers following the that year’s Bush vs. Gore presidential election.

That incident, which is somewhat a product of Democratic folklore, has been used to mock Republican activism as Astroturf, meaning it’s not really grassroots activism but a bought-and-paid-for show by the GOP.

Violent protests are just something that the political right in America doesn’t do. Even the so-called Tea Party movement, which was a reaction to the aggressive policy proposals of President Barack Obama early in his first term, never amounted to any significant violence.

The protesters were often castigated by some in the media as being born of racism. But there was never any looting or any need to deploy the National Guard to restore law and order. In fact, in some cases Tea Party protesters left the venue in which they were protesting cleaner than when they arrived.

Yet the double standard of the media prevailed. Tea Partiers were criticized when one person out of thousands had some protest sign they deemed to be distasteful, like Obama depicted as the Joker of Batman fame or others referencing the birther conspiracy.

When a plate glass window is smashed because of protesters getting out of hand at a World Trade Organization or International Monetary Fund meeting, the media often shrugs the political implications off as just mere acts of anarchy, not really something to be taken seriously.

Many expect that the further along we go into this election cycle, the type of protests that took place in San Jose will become more of a regular occurrence than an anomaly. But that stands to backfire on the Democratic Party.

Some want to compare Donald Trump’s 2016 candidacy to Sen. Barry Goldwater’s (R-Arizona) 1964 effort, in which Goldwater was crushed by incumbent President Lyndon Johnson. But you may see something more in line with the presidential election four years later between Richard Nixon and Hubert Humphrey.

Many attribute Nixon’s success to a backlash against all the protests of the summer of 1968. It was a time when television was just starting to play a role in U.S. politics and the images of violence really dissuaded a lot of Americans from supporting Democratic nominee Humphrey.

Images of protesters waving the Mexican flag as they burn the American flag doesn’t exactly have any widespread appeal. If those images are associated with being anti-Trump, then what’s to stop Hillary Clinton from being tagged with them?

For now the Democratic Party and the left are seen as the movement that engages in violence. Candidates and left-wing mouthpieces, including Democratic presidential hopeful Sen. Bernie Sanders (I-Vermont), have condemned such acts.

But despite those condemnations, the Democratic Party is going to be seen by a lot of voters as the party of civil disorder.

Back in March, Trump warned there could be riots if he was denied the GOP nod at next month’s Republican National Convention. Trump was immediately castigated by some Republicans and many in the media for those comments.

There’s one flaw in Trump’s comments: Republicans historically don’t riot. Now that Trump has all but sewn up the nomination, we will never know if his prediction was accurate, but considering precedent it seems unlikely.

Best to leave inciting violent riots up to the pros, the political and professional left.