When Richard Nixon accepted the Republican Party's nomination in 1968, he was speaking to a country that had seen its violent crime rate spike 80 percent over the preceding eight years and the murder rate increase by a third.

Nixon addressed that increase in his nomination speech. "[T]he nation with the greatest tradition of the rule of law is plagued by unprecedented lawlessness," he said, declaring that "[t]he wave of crime is not going to be the wave of the future in the United States of America. We shall re-establish freedom from fear in America so that America can take the lead in re-establishing freedom from fear in the world."

Crime became a key element of his campaign. In a carefully tailored ad for his candidacy, Nixon argues that he will "take the offensive" against "criminal forces that threaten their peace and security" and that he would "rebuild respect for law" in the United States. "I pledge to you," Nixon says at the ad's climax, "the wave of crime is not going to be the wave of the future in America."

It was. In 17 of the next 22 years, the rate of violent crime increased. That includes every single year during which Nixon served as president.

Happily, that trend changed in the early 1990s. Violent crime rates in 2014, the last full year for which data is available, were still at about the rate the country saw in 1970, but had declined for 20 of the 23 most recent years for which we have data. Preliminary data from 2015 indicates an upward tick in that figure, but it's clear that there's no long-term trend like the one Nixon addressed in 1968.

Nixon's acceptance, though, will serve as the basis for Donald Trump's on Thursday night, according to Trump's campaign manager. "The Nixon 1968 speech — if you go back and read that speech — is pretty much on line with a lot of the issues that are going on today," Paul Manafort said at an event earlier this week. How is it the case that a speech heavily predicated on concerns about crime can serve as a roadmap for a candidate in 2016?

We've noted before that many Americans — 63 percent, to be specific — told pollsters recently that they worried about themselves or a family member ending up as a victim of a violent crime. Trump himself has declared that "crime is out of control." He has declared that he will be the "law-and-order candidate," mirroring Nixon. To what does he point to to prove this? The murder rate in Chicago, of course. But also to protests across the country often linked to the Black Lives Matter movement.

"We have our cities exploded," Trump said in an event in Indiana last week. "We have ISIS looking at us. And by the way, when our enemies all over the world, including our friends all over the world, look at what's happening to our country, where the other night, you had 11 — think of it — 11 cities potentially in a blow-up stage. Marches all over the United States. And tough marches." Trump implied that the marches were inspired by sympathy with the man who killed five police officers in Dallas, without any evidence. But that the Texas killings had followed a Black Lives Matter march allowed Trump to draw a connection.

"[Y]ou see them marching and you see them on occasion, at least, I have seen it, where they are essentially calling death to the police," Trump told Fox News' Bill O'Reilly this week. "And that's not acceptable whether you like them or don't like them, that, Bill, is not acceptable. But I have seen it, and you have seen it."

"In certain instances" Black Lives Matter was inspiring violence against the police, he said. "They certainly have ignited people and you see that. You see it all over. I think it's a very, very serious situation, and we just can't let it happen," he said. He agreed with O'Reilly that the nature of the protests might override the right to assembly.

I have seen them marching down the street essentially calling death to the police. And I think we're going to have to look into that. Especially in light of what is happening with these maniacs going and shooting our police. ...
When you see something hike that taking place, that's really a threat, if you think about it and when you see something like that taking place, we are going to have to, perhaps, talk with the Attorney General about it or do something, but, at a minimum, we're going to have to be watching.

The idea that protesters are regularly calling for the murder of police took hold early in the movement, based on an incident in New York. At other protests, protesters have at times recited chants disparaging police, but in most cases, participants intentionally steer well clear of anything inflammatory. The overlap with police killings, though has reinforced a broad tension between the group and law enforcement.

A new poll from Monmouth University released on Tuesday suggests that people have a divided-but-still-skeptical perception of Black Lives Matter. Americans agree that the movement has brought attention to real racial disparities in society, with 58 percent of registered voters saying it has. But nearly half of Americans also say that the movement has made racial issues in the country worse, including 72 percent of Republicans and 51 percent of independents. (Half of Democrats said it hasn't really changed things either way.)

A poll from Pew Research released in June found that Republicans were least likely to say they supported the movement in any way. Forty percent of white Americans said they support BLM strongly or somewhat; only 20 percent of Republicans are in that camp.

This is obvious at the Republican convention. Speakers have railed against Black Lives Matter, including a speech from Sheriff David Clarke, an outspoken critic of the group.

In short: Trump is seizing on a few incidents loosely or unrelated to a movement about which Americans have divided opinions in order to bolster his case that we're in a 1968-style moment of needing a firm hand. His party is receptive to the argument because it, too, is skeptical of the protesters; independents may be, too. Everyone agrees that isolated violent incidents are disconcerting, but not everyone agrees that there's a link that should be drawn back to the protests themselves. For Trump, that link is hugely useful in an otherwise relatively peaceful moment.

There's obviously a layer of race overlaid here. Trump's got a patchy history on race that his comments about BLM doesn't help. That his party is 90 percent white (according to Gallup in 2013) and given that blacks identify as Democrats by a 7-to-1 margin (per Pew) certainly bolsters the split on partisan perceptions of the movement. Some of the support for Trump is demonstrably rooted in racial tension, as is some of the opposition to BLM.

Nixon knew that racial concerns were at the heart of his arguments on crime, but tried to minimize them. "To those who say that law and order is the code word for racism, here is a reply: Our goal is justice for every American," he said during his acceptance speech in 1968. Trump also brushed aside criticism that he was motivated at all by race.

"I'm doing very well with the African-American community," he told O'Reilly.