It only takes one.
We should know that, but years have passed since April 19, 1995, and many have forgotten or are too young to remember the day the Alfred P. Murrah Federal Building in Oklahoma City was blown up by a truck filled with explosives.
The truck was placed there by Timothy McVeigh, a man whose rage was nurtured by a steady stream of anti-government rhetoric. A man convinced our political system was at war with self-described "patriots" like himself. A man convinced the U.S. government was — to borrow a term we're hearing regularly from GOP presidential candidate Donald Trump — rigged.
The blast killed 168 people, including 19 children and babies. It was the culmination of years of anti-government fervor that had bubbled up during the farm crisis of the 1980s, when economically stressed people in rural parts of the country were wooed by blame-the-feds rhetoric coming from charismatic snake oil salesmen.
I wasn't a journalist when that happened, but I read every story I could find about the tragedy. Once I became a journalist, I spent a year covering the lead-up to McVeigh's execution, and I stood in the media witness chamber and watched him die, his face showing not a hint of remorse.
He was a monster who had been created by our own people, by the ones who filled his head with lies and conspiratorial nonsense.
He was assisted by an old Army buddy, Terry Nichols, but McVeigh was the one who mattered. He was the one nobody saw coming. He was all it took to bring down a building.
Because it only takes one, and that's something we need to remember — right now.
With his presidential campaign flailing, Trump is doing his best to sow doubt about the legitimacy of our electoral process.
"It's one big fix,'' he said at a rally last week. "This whole election is being rigged.''
No, it's not. Reasonable people know that. Republican Sen. Jeff Flake tweeted on Sunday: "States, backed by tens of thousands of GOP and DEM volunteers, ensure integrity of electoral process. Elections are not rigged."
But Trump kept at it, tweeting: "The election is absolutely being rigged by the dishonest and distorted media pushing Crooked Hillary — but also at many polling places — SAD."
He says it over and over now. Rigged. Rigged. Rigged. Many of his surrogates follow suit, including GOP Sen. Jeff Sessions, who said Saturday: "They are attempting to rig this election."
Even worse, Milwaukee County Sheriff David Clarke Jr., an outspoken Trump supporter, tweeted Saturday: "It's incredible that our institutions of gov, WH, Congress, DOJ, and big media are corrupt & all we do is bitch. Pitchforks and torches time." The tweet included a photo of an angry crowd carrying torches, pitchforks and bats.
This is dangerous rhetoric. And it's dangerous because there are people out there like this 50-year-old Trump supporter who was asked by the Boston Globe to consider a Hillary Clinton victory: "If she's in office, I hope we can start a coup. She should be in prison or shot. That's how I feel about it. We're going to have a revolution and take them out of office if that's what it takes. There's going to be a lot of bloodshed."
Late last week, federal agents arrested three men in Kansas — militia members who espoused anti-government beliefs — for allegedly plotting to blow up an apartment complex where many Somali-Muslim people live.
The Washington Post reported: "In the end, they decided to set off bombs similar to the one Timothy McVeigh used in 1995 to kill 168 people in Oklahoma City. They planned to strike after the Nov. 8 election, investigators said."
There is no connection between anything Trump has said and that plot, but his talk of a rigged election, of a scheming media, of hordes of immigrants pouring into the country and of global conspiracies is rich sustenance for twisted minds.
Even the weekend firebombing of a North Carolina Republican headquarters — a shameful attack on democracy — was twisted by Trump into an us vs. them act. Investigators had not said anything about who might be responsible, but Trump tweeted Sunday: "Animals representing Hillary Clinton and Dems in North Carolina just firebombed our office in Orange County because we are winning."
He may be proved right, but to instantly condemn Clinton without a lick of evidence is the height of irresponsibility. (The fact that polls show him trailing in North Carolina is just another example of Trump tossing false information to help rile his followers.)
We are not witnessing normal behavior from a presidential candidate. We are witnessing dangerous behavior.
Monday morning, Trump was at it again, tweeting: "Of course there is large scale voter fraud happening on and before election day. Why do Republican leaders deny what is going on? So naive!"
Coming from a larger-than-life figure running for the highest office in the land, the suggestion that the election might be stolen in some grand, multipronged conspiracy further pollutes unstable minds. Trump's words, whether he cares to believe it or not, are jostling emotional nitroglycerin.
I watched the life drain out of Timothy McVeigh, an unrepentant mass murderer convinced by self-serving fools that he was at war and that his cause was just. I pray there's never another like him.
But let's not forget what happened in Oklahoma City. And let's not underestimate the hatred in the hearts of Americans under the spell of conspiracies and addled views of patriotism.
It can bring down a building.
And it only takes one.