The Donald Trump era in American politics is nearing its fourth birthday, meaning that a lot of things that would once have been shocking to our expectations instead have been worn down to a general category of “remarkable but not surprising.”

Four years ago, we might have expected a U.S. president of either party to respond to a shouted call for killing immigrants with silence at worst and, more likely, a quick, pointed effort to excoriate the shouter and his argument. At Sen. John McCain’s death, one of the most-cited moments from the Arizona Republican’s political life was when he cut off a woman claiming that Barack Obama was an “Arab” during the 2008 campaign. We hope for this sort of nobility — or, at least, hoped for it.

We don’t really expect that from the current president. So when a person at a rally in Florida on Thursday responded to Trump’s rhetorical question about stopping migration into the United States with a shouted “Shoot them!,” we find it remarkable, though not surprising, that Trump sort of chuckled.

"That’s only in the Panhandle you can get away with that statement,” Trump said, referring to the conservative region of the state where the rally was being held.

Of course, there’s no reason the person should have “gotten away” with the statement. It would have been trivial, just the lowest-hanging fruit to say something as anodyne as, “That isn’t funny.” But Trump seems to have thought it was funny, at least sort of. It’s the sort of “not politically correct” thing that Trump himself likes to say.

It also happens to have dealt with a subject where Trump himself is clearly sympathetic to the implication. There have been a number of occasions when Trump has tacitly encouraged the idea that migrants seeking to come to the country were dangerous and should be dealt with harshly.

At his campaign launch, he infamously disparaged migrants entering the United States from Mexico as “people that have lots of problems, and they’re bringing those problems with us.”

"They’re bringing drugs. They’re bringing crime. They’re rapists,” he said. Some, he added, were good people. Most, he implied, weren't.

Trump himself has hinted that he wishes the military could use force to repel those allegedly dangerous migrants at the border. In April, he lamented that it couldn’t do so during a visit to Texas where he talked about sending more troops to the border.

“Our military, don’t forget, can’t act like a military would act,” he said. “Because if they got a little rough, everybody would go crazy.” That danged political correctness again.

In November, with the midterm elections looming, he seemed to encourage violence despite the obvious political blowback. He was asked if the troops he was sending to the border were authorized to use lethal force. He suggested that they could, if those at the border threw rocks at the troops.

“If they want to throw rocks at our military, our military fights back. We’re going to consider — and I told them, consider it a rifle,” he said. “When they throw rocks like they did at the Mexico military and police, I say, consider it a rifle.”

The implication? Troops were authorized to open fire. He later backed off that comment. But he did tell Fox Business Network’s Maria Bartiromo last month that toughness of questionable legality was all but necessary.

“When you get cute, when you get tough, when you do all of these things that we have to do,” he said, “they end up arresting Border Patrol people.”

In July 2017, he gave a speech on Long Island focused on the purported threat posed there by members of the criminal gang MS-13 — a group, he asserted, that overlapped heavily with the migrant community. He made reference to his claims at the campaign announcement that immigrants were dangerous and gave some advice to the police officers in attendance.

"You see these thugs being thrown into the back of a paddy wagon — you just see them thrown in, rough — I said, please don’t be too nice,” he said. “Like when you guys put somebody in the car and you’re protecting their head, you know, the way you put their hand over? Like, don’t hit their head and they’ve just killed somebody — don’t hit their head. I said, you can take the hand away, okay?”

Many Americans won’t complain about accused criminals being treated harshly, even those not convicted of any crime. Trump, though, intentionally conflates criminal groups (such as the U.S.-born MS-13) with immigrants broadly. As when he said during that speech on Long Island that MS-13 had “surged” into the country — than stating that “more than 150,000 unaccompanied alien minors arrived at the border” in the three years before he took office “and were released all throughout our country into United States communities — at a tremendous monetary cost to local taxpayers and also a great cost to life and safety.”

There's no indication that any significant percentage of those migrants committed crimes.

Of course he has repeatedly continued to claim that those migrants seeking entry to the United States are dangerous. During the political fight over his proposed border wall, he and his administration linked migrants to human smuggling, violence, gangs and terrorism — generally using inflated or misleading data to make that case. It’s not just migrants at the southern border who’ve been subject to that treatment, either. Trump has repeatedly linked migrants from predominantly Muslim countries to the threat of terrorism.

The recent increase in migrants arriving at the border began on the watch of then-Homeland Security Secretary Kirstjen Nielsen. Her relationship with Trump had been rocky for some time, with his feeling that she wasn’t holding a sufficiently tough line against those seeking entry into the United States.

When her resignation was announced, The Washington Post reported that she had regained Trump’s favor at one point.

“She appeared to regain her footing after U.S. Border Patrol agents used tear gas to repel a large crowd attempting to break through a border fence — the kind of ‘tough’ action Trump said he wanted in a DHS secretary,” The Post reported.

Remarkable but not surprising.