What happened at the foot of the Lincoln Memorial last Friday isn’t entirely clear. A large group of high school students from Kentucky, in town for the antiabortion March for Life rally, were gathered there waiting for school buses that would take them home. A small group of Black Hebrew Israelites were there, too, as were participants in the Indigenous Peoples March, held that same day.

You’ve probably heard the story of what happened by now — or, at least, a story. Perhaps you heard that the high school kids from Covington Catholic were being taunted by the Hebrew Israelites and responded with what were described as chants for their school sports teams, the Colonels. Perhaps you saw a video of a Native American man walking between the two groups, singing and beating a drum. Perhaps you saw him later standing face to face with one of the students, who was smiling and unmoving. And you probably read at least one of the scores of stories in which the Native American elder, Nathan Phillips, was quoted or included a statement from the student, Nicholas Sandmann.

Omaha elder Nathan Phillips and high school student Nick Sandmann give their versions of viral moment on the steps of the Lincoln Memorial. (Erin Patrick O'Connor, Joyce Koh/The Washington Post)

Even over a holiday weekend, varied opinions of that unexpected encounter spread quickly across the country. On Monday, after seeing a report on Fox News, President Trump weighed in — unequivocally on the side of the students and Sandmann. Trump hyped allegations that the initial response to news of the event, a response that generally criticized Sandmann and the other students as mocking Phillips, was unfair or inaccurate. On Tuesday, Trump continued that theme.

Again, the exact nature of the incident is unclear, with parties on all three sides offering conflicting claims. But there are several obvious political reasons that Trump has been quick to weigh in on behalf of the students.

Trump’s base is heavily predicated on support from Americans who identify as religious. We’ve all internalized by now that Trump’s core base of support is white Americans without college degrees. Research compiled last year, though, adds a slightly different perspective: The core of the group that is most loyal to Trump also identifies as evangelical Christian.

“The gap between white voters who approve and disapprove of Trump by gender was 25 points. By education (college versus non-college) it was about the same at 26 percent,” the Cook Political Report’s Amy Walter wrote last year about analysis of data from the Public Religion Research Institute. “But the gap in perceptions of the president between white voters who are evangelical and those who aren’t was a whopping 60 percent!”

Independent of other demographic distinctions, identification as an evangelical was a strong predictor of support for Trump.

Evangelical voters are not necessarily sympathetic to the plight of American Catholics, of course. But the fact that the boys from Covington were in Washington for the March for Life is significant. Opposition to abortion is a central motivating issue for many Trump supporters, including evangelical voters.

Trump supporters are much more likely to view white Americans as threatened. Donald Trump Jr., the president’s son, made a startling claim last year. He said he was more concerned about the future of his sons than of his daughters, given an environment in which unfounded accusations might be made against them.

This attitude is echoed in how Trump’s base views groups that are traditionally considered to be in enviable positions in the United States — positions of privilege, if you will. One of the defining components of Trump’s campaign was that his base was much more likely to say they’re worried about “reverse racism” — that is, racism targeting white Americans. In a 2016 HuffPost/YouGov poll, more Trump supporters said whites were discriminated against than said the same of Muslim, black or Jewish Americans.

Such views mirror the evangelical community’s. Another PRRI survey found that more than half of that group said the United States’ becoming mostly nonwhite would be a negative development for the country.

It’s impossible to extricate race from Friday’s events. All sides agree that it involved a group of white high school students, many wearing Trump’s signature “Make America Great Again” hats, in a loud confrontation with a group of black protesters who then turned their attention to a Native American man who walked into their midst. The fact that the high school students were immediately blamed for the confrontation was apparently interpreted by many as another sign that the white participants were targeted unfairly.

Trump gets to blast the media for its behavior. That blame of the students, many felt, was a function of media bias. As Trump’s tweet on Tuesday makes clear, he’s enthusiastic about linking the negative attention they garnered to unfair rushes to judgment by media outlets and journalists. But as more videos of the confrontation were published, outlets including The Post offered more nuanced looks at what happened.

That sort of self-adjustment is expected of media outlets, but it can also be weaponized. In the eyes of Trump and many of his supporters, the media at large rushed to judgment against the teens, who many assert have been all but exonerated. (That’s not true, either. In addition to the murkiness of the initial clips, additional videos purporting to show the same teens engaged in questionable behavior at other points during the day have been published on social media.) Sandmann released a statement in which he made a case for his own victimization in initial interpretations of the confrontation, and his supporters have eagerly identified the media as the victimizers.

Trump needs this. Over the course of the month-long government shutdown, Trump’s approval rating has sagged. When the shutdown began, on Dec. 21, his average disapproval rating in polls compiled by RealClearPolitics stood at 51.8 percent. As of Tuesday, it stands at 55.6 percent, the highest it has been since March.

By focusing on an issue that motivates his base instead of on the shutdown, for which he’s broadly taking the blame, there is little political downside for the president.

He knows the playbook will work. If all of this seems familiar, it should. MSNBC’s Chris Hayes made an interesting observation on Twitter.

That fight, over the nomination of Brett M. Kavanaugh to the Supreme Court, was similar in broad strokes to the debate over Covington Catholic. It centered on the behavior of a student at an all-boys Catholic school — in that case, Kavanaugh himself — and what were described as false accusations against him perpetrated by the media. That fight helped galvanize the right, even if it didn’t necessarily help Trump all that much.

This fight is more potent, in part because it focuses on the same sorts of young men for whom Trump Jr. expressed worry. (Trump Jr.'s comments were a response to the Kavanaugh fight.)

It was not predetermined that Trump would seize upon Friday’s altercation, of course. He could have chosen to sit it out, to let the furor over the events on the Mall dissipate. No one, though, should be surprised that he did engage — and he did so in part because of how many hot buttons he gets to press.