In the wake of two horrific mass shootings over the weekend, particularly the one in El Paso where 22 people were allegedly murdered by a man who apparently left an online message echoing some of the themes of President Trump's rhetoric, many have been putting blame at least partially at the president's feet. We can debate how justified that is, but for the moment I want to shift focus just a little. There's another vital question we need to ask: not whether Trump is inspiring murderers, but whether he is now, and will in the future, disappoint them in ways that could lead to more deadly violence.

In that screed, the author made reference to "the great replacement," a right-wing theory about how white people are being replaced not only in numbers but in power and influence by minorities. The neo-Nazis who marched in Charlottesville in 2017 chanted "Jews will not replace us!" These ideas are heard on the president's favorite cable news network, where Laura Ingraham warns that Democrats "want to replace you, the American voters, with newly amnestied citizens and an ever increasing number of chain migrants."

"This attack is a response to the Hispanic invasion of Texas," the author wrote, stressing the importance of forestalling future Democratic electoral victories. But he did not cite Trump as his inspiration or his savior.

"My opinions on automation, immigration, and the rest predate Trump and his campaign for president," he wrote. Trump has been president for almost three years, talking in the same way this young man allegedly did and identifying the same thing as America's most serious problem. Yet as far as the author was concerned, the Trump presidency didn't solve that problem. Mass murder was still required.

In 2016, with his disturbingly sharp instinct for locating and stimulating the worst in people, Trump understood something other Republicans missed. The party's base was angry and hungry, hungry for someone who would dispense with dog whistles and insinuations and give explicit voice to their rage and resentments.

For many of them, that's enough. To hear their sentiments echoed from the highest office in the land provides enormous satisfaction, even if the results don't match the rhetoric.

But others, the less stable and the more heavily armed, will not be assuaged. They may well see in Trump's presidency nothing but failure. After all, didn't he promise a return to when people like them were on top? The Muslims would be banned, the minorities would be shown their place, a "big beautiful wall" would be built from the Pacific Ocean to the Gulf of Mexico — and Mexico would pay for it.

It's hard to overstate the symbolic importance that last part had for many Trump supporters, even if it was preposterous. The idea of forcing Mexico to pay for the wall was about dominance, restoring our dignity by humiliating our neighbor to the south. This was the beating heart of what Trump promised, especially to white men who felt the world had shoved them aside: a restoration of strength and stature.

And if you were one of those men, what do you see around you? You might love Trump for the things he says, but you might also come to believe he has failed you.

America has not been cleansed. The wall is not built, and Mexico has paid for nothing. Trump has not stopped the "invasion" or the "infestation"; instead, on an almost daily basis, he tells us it's getting worse. Muslims are still here; a few of them are even in Congress. Women keep occupying more positions of prominence and insisting that men be held to account for behavior that once was seen as their privilege.

If that's what you think, you may or may not be angry at Trump, but you may conclude that it was foolish to expect a president to accomplish what you thought was needed. And you might, like the alleged El Paso or Tree of Life shooters or any of the white supremacist/nationalist terrorists we've seen in recent years, decide that you have no choice but to take matters into your own hands.

As historian Rick Perlstein noted just after the 2016 election, Trump made practical promises he couldn't possibly keep, but "the biggest, only made implicitly, was the same one fascist strongmen always offer: transcendent national renewal, built upon the cleansing of dangerous untermenschen from the body politic." Once that promise inevitably fails to be fulfilled, the results could be catastrophic. Perlstein wrote: "The more Trumpism fails, the more, and more violently, scapegoats will be blamed."

We are not heading toward that point, because we're already there. And what happens if Trump loses in 2020? Then the most radical and murderous on the far right will know that the political project truly failed, and they may decide there is no option but violence until the America they want is born out of the carnage.

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