It is unfair to blame President Trump for any specific act of political violence. Much like it is hard to blame global warming for any particular weather event. But the climate — political and literal — is changing. The context in which a disturbed mind decides to construct bombs rather than just paste another bumper sticker on his van is shifting. Humans have added ever-more heat into the system. The extra energy exacerbates problems that might have occurred naturally. Extreme events are more likely. And Trump is responsible for that.

It takes a troubled intellect to send bombs in the mail. Trump cannot be blamed for whatever mental defect led the perpetrator to resort to terrorism. Yet if the FBI caught the right man when federal investigators arrested Cesar Sayoc in the attempted bombings of several prominent Democrats, it is relevant that his confiscated van was covered in pro-Trump slogans, pictures of the president and anti-mainstream media messages. Even if Sayoc did not send the bombs, it is relevant that the targets are people the president has singled out for condemnation. Maybe the bomber would have drawn up this list on his own even if the president had not harassed these specific people. Maybe some fringe right-wing website would have inspired the attacks, regardless of the president’s words. Maybe.

But the fact that it is so plausible that Trump inspired this crime is its own indictment of the president. He conveys the conspiracy-laden messages of those right-wing websites, just this week implying that the bomb attacks might have been a false-flag plot to harm Republicans in the midterm elections. Trump has made it harder to believe that Americans’ differences are resolvable, or even that those who decline to bow to him deserve the right to do so. They are an angry mob. They want to subvert the nation’s democracy. They are enemies of the people. They should be locked up. They should be bodyslammed. They have committed treason.

Anyone listening credulously to Trump over the past two years would conclude that the bombing targets — the Clintons, the Obamas, former CIA director John Brennan, Democratic donor George Soros and others — are part of a dark anti-American conspiracy aimed not just at harming Trump but also at turning over the country to mobs and foreigners. They are not people who are, in his telling, merely wrong. They are illegitimate actors maring our national stage. They are evil.

When a gunman shot and nearly killed House Majority Whip Steve Scalise (R-La.) last year, the assault was not just an attack on Republicans, but on the U.S. Congress and the principle that divisions in a diverse nation can be resolved peacefully. When someone sent a letter claiming to be laced with ricin to Sen. Susan Collins (R-Maine) for her vote to confirm Justice Brett M. Kavanaugh, it violated the notion that lawmakers face nothing more dangerous than losing an election for conducting that work.

This week’s attempted bomb attacks are an assault on another crucial principle of any free society — that those who oppose the current government do not have to fear for their physical safety.

The uncomfortable truth is that they have more to fear these days. Of all these episodes of political violence, the mail bombs come closest to implicating a political leader. And that politician is, sadly, the president of the United States.