This is a perilous political moment for President Donald Trump, which means that it's time to pay a visit to the well of resentment and hatred that got him to the White House.

This week, the president has promoted two stories — an imagined oppression of white farmers in South Africa and the murder of an Iowa woman named Mollie Tibbetts. His actions offer a vivid illustration of how he and the entire conservative movement use race-baiting to keep the Republican base in a state of agitation and anger. The move takes the focus away from issues that could weaken the standing of the president and his party.

We'll start with the Mollie Tibbetts story, which has a familiar ring: A young white woman allegedly murdered by an immigrant, whom the president then uses to argue for both immigration restrictions and the election of more Republicans. Here's what Trump said at a rally this week in West Virginia:

"You heard about today with the illegal alien coming in very sadly from Mexico, and you saw what happened to that incredible, beautiful young woman. Shoulda never happened. Illegally in our country. We've had a huge impact, but the laws are so bad. The immigration laws are such a disgrace. We're getting them changed, but we have to get more Republicans."

We should note that whether the suspect is actually undocumented is in dispute. And you'll notice that, as he always does in these cases, Trump describes the victim as "beautiful," as though her death might be less of a tragedy had she been less attractive. But how did this story get on Trump's radar?

The answer lies in the fact that Trump is not an outlier within the GOP. It's not as though he dragged an unwilling party toward the use of race-baiting as a core political tactic. He's only the most visible manifestation of a strategy that reaches back decades and today is on a constant hair-trigger.

There's a network of conservative media outlets and political figures always on the lookout for ways they can promote hate, fear and resentment among white people. When something like Tibbetts' murder happens, they swing into action. Trump's own involvement actually comes only after he has been alerted to the case by this network.

On Wednesday, the morning of that rally, Axios reported that “Former Speaker Newt Gingrich emailed Axios' Mike Allen to make sure that we’d be covering” the Tibbetts story, which was already in heavy rotation on Fox News. Gingrich — who is more responsible than any other single figure for America’s slide into vicious, bitter partisanship over the last couple of decades — explained that “If Mollie Tibbetts is a household name by October, Democrats will be in deep trouble. If we can be blocked by Manafort-Cohen, etc., then GOP could lose [the House] badly.”

In other words, the danger for Republicans is that the news media might pay too much attention to one of the largest presidential scandals in decades and not enough attention to the story of one young woman’s murder. They’re doing what they can to forestall that possibility: I searched this morning on foxnews.com for Mollie Tibbetts' name and came back with a remarkable 192 results — 192 separate stories and videos about this case.

In 2016, the last year for which we have complete data, there were 17,250 homicides in America, so Tibbetts' murder is one of a huge number of tragic stories of violence that could draw national attention at any given moment. And as you've probably heard by now, we know that immigrants in general, and undocumented immigrants in particular, commit fewer crimes than native-born Americans do.

But when conservatives decide immediately upon hearing about it that this is the story they want to call attention to, they aren’t doing it because of their commitment to stopping crime. They’re doing it because it gets Republicans mad — an anger that was the basis of Trump’s victory and is the foundation of the business model for Fox News and other conservative media outlets.

On Wednesday, the White House tweeted out a video featuring family members of people killed by undocumented immigrants, whom they say were "permanently separated" from their loved ones, a direct reference to the Trump administration's family separation policy at the border. The linking of these isolated cases with the policy of taking children from the arms of parents seeking asylum almost seems to posit that policy as a kind of revenge taken out on immigrant families for crimes other people have committed, or at the very least setting up a ludicrous and repellent moral hierarchy: Sure, we're traumatizing children and parents, but it's better than killing the children, right?

Now let's turn to the second issue Trump decided to draw attention to this week: a white supremacist conspiracy theory. On Wednesday he tweeted:

"I have asked Secretary of State @SecPompeoto closely study the South Africa land and farm seizures and expropriations and the large scale killing of farmers. 'South African Government is now seizing land from white farmers.'"

Sen. Bob Corker called the tweet a “base stimulator,” and when asked what that meant, he replied, “Well, there are portions of those who support the president that are — I’m sure that generates excitement. I mean, it’s — you know what I’m saying.”

Indeed we do.

Where did the story come from? A pipeline of hate that pours its effluent into the Oval Office. For years, white nationalists, alt-righters, neo-Nazis and other assorted deplorables have been complaining about an alleged "white genocide" occurring in South Africa around the issue of land reform. From various Internet chat rooms, the cause was taken up by right-wing hucksters like Ann Coulter and Mike Cernovich.

Then Wednesday, Tucker Carlson did a segment about it on his Fox News show, which Washington Post media critic Erik Wemple says might be better titled "Your hour of white grievance." Trump watched and sent out his tweet, and the result is a minor diplomatic crisis.

Naturally, white nationalists are elated that Trump has taken up one of their pet causes. But they may not realize that he couldn't care less about South African land reform. By next week he'll have forgotten all about it, just as he'll forget all about Mollie Tibbetts once she's been replaced by another "beautiful" white girl whose death he can exploit for political ends. The only constant is that he'll keep looking for new ways to keep white voters angry and afraid, in the hopes that it can save him from whatever political peril he faces.

Which is why it may only get worse.

Paul Waldman | The Washington Post

Paul Waldman is an opinion writer for the Plum Line blog.