Acts of murderous political violence are not new in America. In and of themselves, they do not tell us much about the state of the country and its political culture.
What's revealing, however, is how Americans respond, and the political meaning we ascribe to senseless acts by madmen.
There is appalling symmetry in the fact that James Hodgkinson III of Belleville, Illinois, tried to massacre baseball-playing Republican lawmakers shortly after the first anniversary of the deadliest mass shooting in modern U.S. history. The perpetrator in that case was Omar Mateen, a 29-year-old Afghan-American influenced by pro-Islamic State propaganda who targeted an Orlando, Florida, nightclub frequented by gay men.
In the wake of that slaughter, in which 49 people lost their lives and 58 others suffered injuries, Gallup asked Americans: Do you view the incident in Orlando over the weekend as more an act of Islamic terrorism or domestic gun violence?
The responses followed a clear partisan pattern: By a margin of 79 percent to 16 percent, Republicans considered the attack "Islamic terrorism"; by a margin of 60 percent to 29 percent, Democrats saw it as "domestic gun violence."
Thus did the Orlando massacre pass into contemporary American history as a terrible tragedy, a grotesque crime - and yet another example of the country's division into political tribes, seemingly incapable of formulating a common view of reality, let alone a common approach to public policy.
Of course, Gallup's prompt was a bit of a trick question. The best answer would have been some version of "both," or maybe "all of the above." Mateen was a U.S. citizen, an Islamist extremist, mentally unstable and all too authorized, under federal and state law, to get his hands on deadly firearms.
A similar blend of lessons apply to Hodgkinson, a deranged follower of Sen. Bernie Sanders, I-Vt., with an apparent history of domestic violence. He would have been a mass murderer on a numerically smaller, but politically more devastating, scale than Mateen - if not for some blind luck and the courageous intervention of police officers.
Mentally calculate the shock Washington and the nation felt from Hodgkinson's wounding of a member of Congress, a congressional staffer, a lobbyist and a Capitol Police officer. Now multiply that by the spectacle of a baseball field strewn with the bodies of a sizable percentage of the Republican majority on Capitol Hill, as the shooter apparently intended.
Absolutely no one is responsible for this deed except the individual who carried it out. And the list of the non- responsible very much includes the shooter's political idol, Sanders, who eloquently repudiated the assassination attempt, noting, correctly, that "real change can only come about through nonviolent action."
Everyone, though, is responsible for what he or she makes of this event after the fact. Each of us has it within his or her power to exploit it - as some predictably rushed to do on social media - or to learn from it.
Sanders' speech found soothing and lofty echoes in the remarks of President Donald Trump, who said that "everyone who serves in our nation's capital is here because, above all, they love our country." Perhaps the day's most affecting statement came from House Minority Whip Steny Hoyer, D-Md., who referred to the seriously wounded Rep. Steve Scalise, R-La., as his "friend," even though Scalise is much reviled among progressives.
"I hope everyone in our country will take time today to reflect on how our commonalities far outweigh our differences and that we all share in the work of this grand experiment in democracy," Hoyer added.
Who could fail to share that hope? Yet it's just stating the obvious to note that Trump's statesmanlike words, read from a teleprompter, were of a much different tone than many of his past utterances at rallies and on social media. Or that Trump-hatred has reached irresponsible extremes of which Kathy Griffin's sick decapitation joke was only one example.
To be sure, harsh and even violent rhetoric has an ancient pedigree in American politics. We live in a time, however, when the way to get ahead in politics is to attack not just the political center, but the very idea of a center. Consensus itself is held to be corrupt, a mere cover for the "rigged system" or "deep state" underneath.
To repeat, even rough-and-tumble rhetoric, even stupid, vulgar demagoguery, does not necessarily incite violence.
Yet in times of polarization, the constant barrage of such words can, and does, deplete reservoirs of trust that society must draw upon in response to violence.
Those reservoirs were running dangerously low even before Wednesday.