The Republican National Convention will begin this Monday, July 18, and end on Thursday, July 21.

The Democratic National Convention will begin the Monday after that, July 25, and end on Thursday, July 28.

The Three Weeks that lead to Tisha B’Av, when observant Jews fast, sit on the floor, and listen to the haunting, beautiful melody and haunting, horrifying words of Eicha, the Book of Lamentations, begins on the evening of Saturday, July 23. (Tisha B’Av starts this year on the evening of Saturday, August 13.)

Surely, the way that those things fall, the American political events and the Jewish ones, are coincidental. Still, we can learn from them.

The monstrous images in Eicha — withered young men and women struck down in what should have been their prime, desperate mothers eating their own children — are meant to be a cautionary tale. The strongly visual words enter our heads on the wings of the plaintive music, and they get stuck there, forever part of our own internal library of horror. The book ends with hope, but it gets there slowly, and the price is terribly high.

We are taught that the reason for the siege and fall of Jerusalem, the most basic of the historical nightmares said to fall on Tisha B’Av, was sinat chinam. Senseless hatred; the hatred for one Jew against another, the willingness to allow that hatred out of the limits of the Jewish world and to infect the Romans as well.

The echoes of that ancient tragedy lap up against the walls of the debacle playing out now on our national stage.

Political campaigns are not for the thin-skinned or faint-hearted. That’s always true. Politicians — successful politicians, at any rate — have to master the art of the bland insult, the rapier put-down, the blunt insult, along with the ability to be polite and at least pretend to listen to pompous blathering while eating very bad chicken. Those are necessary skills. A certain amount of invective aimed at opponents always seems to be necessary as well.

But the level of insult, of nastiness, of crudeness, of second-grader potty-mouthedness, has reached a new level during this campaign, and now we see it as having consequences.

A raft of gun violence has riveted the nation, culminating in the deaths last week of two black men by police officers, and then with one deranged gunman, who was black but more saliently, it seems, also absolutely crazy and armed to the teeth, who murdered five police officers, because they were white.

A few weeks before that — on Shavuot, in fact — a deranged Muslim gunman killed 49 people, mostly Latino, mostly gay or lesbian.

The gunmen were insane, their arsenals were insane, and they might have committed their crimes anyway, but it is easy to think that the climate of hatred and fear fomented by the unhinged sounds of the presidential campaign made it all worse.

If this is not sinat chinam — senseless hatred — it is hard to see what might be. We — we Americans, that is, the larger body politic — are encouraged to hate everyone different from us — Mexicans, immigrants, black or white people, perhaps even, in a dog-whistle-y nod-nod-wink-wink kind of way, Jews.

It didn’t work for the Jews of Jerusalem, and it won’t work for us. All that can work is the attempt to overcome senseless hatred, to see each other as real people, each one of us just trying to do our best, to make sense of our world, to hang on, to hold on, to keep going.

If we can do that, if we can model ourselves after Dallas’s police chief, David Brown, who feels the despair but refuses to give into it; who confounds easy categorization because he is both black and the city’s top policeman, and if we can model ourselves after Dr. Brian Williams, who is the trauma surgeon in Dallas who was unable to save the police officers, and whose pain as a doctor, a black man, a father, and a feeling human being was so palpable we could feel it all the way here; if the political conventions can end without violence, with genuine policy disagreements but without name-calling, without petulant nicknaming and churlish curled-lip threats; if we somehow can head into the election with at least some dignity and decency intact, then, like Jews at the end of Tisha B’Av, we can walk blinkingly but hopefully into the future.

Then, if those things happen, then, like Jews in the week after Tisha B’Av, we can take comfort in the soft autumn that will follow the harsh summer. Nachamu. We will be comforted.