‘The whole world is watching,’’ the cry from streets of Chicago during the 1968 Democratic National Convention, is being repeated today as Donald Trump appeals to extremism and warns about riots if there is a contested convention this summer. Although it was determined that the demonstrations in ’68 were a “police riot,’’ voters blamed the protesters and chose Richard Nixon over Hubert Humphrey, with 13 percent voting for the segregationist Governor George Wallace. In today’s campaign, Trump incorporates Nixon’s appeal to the “silent majority’’ with the menacing qualities of a Wallace rally. He flirts with the Ku Klux Klan, calls Mexican immigrants rapists and murderers, pledges to deport Muslims and other immigrants, disdains Megyn Kelly for “bleeding from wherever,’’ glorifies punching anyone who disturbs his peace, and scapegoats those protesting his views for taking away his right to free speech.

Can’t anyone remember the judicial wisdom that shouting fire in a crowded theater is illegal incitement? That’s the road we are on. Trump is deliberately provoking all this and, if it goes on, there is likely to be bloodshed and blame.

In 1968, deep public foreboding arose in Chicago during the days of violence following the April murder of Martin Luther King Jr., with Mayor Richard J. Daley issuing shoot-to-kill orders. As the August Democratic convention approached, I could feel the danger of police oppression building up.

As one of the leaders of the protests during the convention, I was shadowed constantly by undercover police, and was beaten and arrested. In the police van, those same officers told me I would be indicted and sent to prison. The indictments of eight of us on conspiracy and incitement to riot charges came in 1969 from Nixon’s attorney general, John Mitchell (who later was imprisoned after Watergate).

The FBI had supplied faked “intelligence’’ to anxious Chicago officials about “threats’’ ranging from an armed black takeover of the city to yippies dropping LSD into Lake Michigan while fornicating on the beaches. City Hall suspended all permits for events, including a rock festival, a Eugene McCarthy rally, and a large demonstration outside the Convention Center. The city disconnected sound systems, pulled the permits, and ordered that no one could sleep in the parks, leaving protesters few options other than to stay on streets or leave town.

This led to a cycle of police tear-gassing and assaults, including 63 police attacks on reporters.

In the aftermath of the convention, US Attorney General Ramsey Clark chose not to seek federal indictments against the protesters. However, after Nixon was elected on a law-and-order platform, Attorney General Mitchell indicted the so-called Chicago Eight, myself included. The trial ended five years later with our acquittals, but the damage was done. Most Americans believed the protesters were to blame.

Another cycle of hysteria and political violence happened at Kent State and Jackson State universities two years later. Republican officials kept warning of anarchy, especially after Nixon’s sudden invasion of Cambodia. Nixon and John Dean stirred the flames in hopes of electing Governor James Rhodes in a tight Republican primary for US Senate in Ohio. Rhodes declared the students protesting martial law were “worse than brownshirts.’’ Days later, at a peaceful protest at Kent State, the Ohio National Guard shot and killed four student protesters. The next week, two were killed in a protest in Jackson, Miss.

Nixon later order a commission to study campus unrest. Called the Scranton Commission, the study concluded the shootings were “unnecessary, unwarranted, and inexcusable.’’ Further, the report warned that the “crisis has roots in divisions of American society as deep as any since the Civil War.’’ Once again, despite the evidence, the politics of law and order prevailed.

What can a veteran of 1968 like myself counsel to those who are protesting against Trump? I have watched the rising conflicts at Trump events with a growing foreboding but also with relief that the protesters are standing up for their dignity against insults.

But this is not about clashing street armies or arm-wrestling. This is about rival narratives.

My message to the anti-Trump protesters today is: Don’t surrender to the bullying, but also don’t play into the bully’s game plan. That can lead to political disaster, like the 60 percent majority for Nixon and Wallace in 1968. Be fully aware that there are paid informants and provocateurs in your midst. Work toward a united front against Trump, building bridges without bruises.

Some of you might file a lawsuit charging the Trump campaign with incitement in the name of his “love fest.’’ Public forums could begin at once to gather testimony about the scale and tone of Trump’s berating of most Americans, including his promises to punch people in the face. A bill of particulars might be taken to the steps of Congress and circulated globally. A growing indictment against incitement may pressure Trump to back down and refocus on promoting capitalism. Or the Republicans might find another candidate.

In any event, it’s door-knocking, not fist-fighting, that will settle the outcome.

Tom Hayden is an author and activist. He served in the California State Assembly for 18 years.