Could Donald Trump be held legally responsible for inciting violence at his rallies?

On Aug. 11 of last year, Donald Trump reacted to an incident in which Black Lives Matter protesters seized a microphone from Bernie Sanders. "That will never happen with me," he said. "I don't know if I'll do the fighting myself, or if other people will. It was a disgrace."
On Oct. 23, a Trump rally in Miami was consistently interrupted by protesters. Trump explained his strategy to the crowd. "See the first group, I was nice. Oh, take your time. The second group, I was pretty nice," he said. "The third group, I'll be a little more violent. And the fourth group, I'll say get the hell out of here!"
On Nov. 22, Trump responded to an incident in which a protester was roughed up by people at a rally. "Maybe he should have been roughed up, because it was absolutely disgusting what he was doing," Trump said. "I have a lot of fans, and they were not happy about it. And this was a very obnoxious guy who was a trouble-maker who was looking to make trouble."
On Dec. 12, the campaign began playing an announcement at the start of campaign rallies. "If a protester starts demonstrating in the area around you, please do not touch or harm the protester," an announcer states. "This is a peaceful rally." When it was played at a rally in Feb., a reporter noted that the audience laughed.
On Feb. 1 of this year, Trump says that his security team told him someone in the audience was preparing to throw tomatoes. "If you see somebody getting ready to throw a tomato, knock the crap out of them," he said. "Just knock the hell out of them. I promise you, I will pay for the legal fees."
On Feb. 23, Trump spoke at a rally in Las Vegas and mentioned an incident with a protester. "Here's a guy, throwing punches, nasty as hell, screaming at everything else, when we're talking...," he said. "I'd like to punch him in the face, I tell ya."
He continued. "You know what I hate? There’s a guy, totally disruptive, throwing punches, we're not allowed to punch back anymore. I love the old days. You know what they used to do to guys like that when they were in a place like this? They’d be carried out on a stretcher, folks," Trump said. Later, he drew an analogy to waterboarding, which had come up in a debate.
"They said to me, 'What do you think of waterboarding?'," he said to the crowd, which was chanting "U-S-A!". "I said I think it’s great, but we don't go far enough. It’s true. We don't go far enough. We don't go far enough."
On Feb. 27, he criticized the slow reaction of police in ejecting protesters. "You see, in the good old days, law enforcement acted a lot quicker than this," he said. "A lot quicker. In the good old days, they’d rip him out of that seat so fast — but today, everybody’s politically correct."
On Wednesday, a protester being escorted out of a Trump rally was sucker-punched in the face by an audience member. This was not the first incident in which protesters had been physically attacked -- not even this month. At the Republican debate the following night, Trump was asked about incidents of violence at his rallies, and he blamed the protesters. At a press conference on Friday morning, Trump repeated the same argument he'd made in the past.
"He was swinging, he was hitting people, and the audience hit back," Trump said about an unspecified protester. "That's what we need more of." (A CBS reporter who follows the Trump campaign tweeted last night that he had "yet to see a single protester start swinging as Trump just said.")
There's a reason we've documented those comments in the way that we have. To a casual observer, it gives the impression of a candidate that is, at times, explicitly encouraging violence against protesters at his rallies. This is perhaps not every example; Trump has held many rallies and protesters appear at most. But it suggests a pattern to a lay person.