On Sunday, in the wake of two more horrific mass shootings, one inspired by the hateful replacement conspiracy-mongering that casts immigrants as “invaders” and less than human (e.g., “infestation,” “animals”), the Democratic presidential candidates seized the high ground and, in the absence of a president who could exert moral leadership, directed attention to the central challenges we face: A white nationalist-supporting president and a country flooded with semiautomatic guns. The toxic combination has created a pandemic of hate crimes and mass violence the likes of which we have never experienced in America.

The candidates grasped the moral seriousness of the moment. Sen. Cory Booker (D-N.J.) was impressive:

Sen. Kamala D. Harris (D-Calif.) likewise rose to the occasion on guns and the president’s noxious influence:

Beto O’Rourke, who served El Paso in Congress, was on the scene, assuming a presidential presence —meeting with victims, heralding his community and calling out hate and racism — when the actual president was golfing:

It was quite a transformation from last week’s debates in which candidates were scolding one another and castigating President Barack Obama’s legacy rather than focusing on President Trump. Sen. Kirsten Gillibrand (D-N.Y.) dredged up a nearly 40-year-old op-ed to accuse former vice president Joe Biden of opposition to working women, an accusation so at odds with what we know of Biden — a single father after losing his first wife, married to Dr. Jill Biden, advocate of issues such as equal pay — that it not only fell flat but also made Gillibrand seem desperate. Likewise, attacks on Obama, the author of the Deferred Action for Childhood Arrivals, for excessive deportations sounded weird when the current president is ripping children from parents arms and stoking white nationalism. And after Dayton and El Paso, these tactics seem even more ludicrously tone deaf.

The necessity for finding the best standard-bearer to take down Trump and the moral seriousness of the moment, should prompt a truce on Democrats’ gotcha attacks and opposition research dumps on fellow Democrats (whose differences are tiny compared with the gulf between them and Trump). Surely, they can argue the merits of their positions civilly, but they should acknowledge that the one acting in bad faith on a range of issues is in the White House.

The debates have done nothing to shake up the race because they have not fundamentally altered the perception, right or wrong, that Biden is a solid, decent, plain-wrap Democrat who can beat Trump. Attacking his character turns out to be fruitless; attacking the Obama era as a colossal policy failure turns out to be dumb.

Candidates seeking to overtake Biden won’t do so by castigating Obamacare as a front for Big Insurance or attacking deportations aimed at criminals (as was the case in the Obama presidency) or by promising another revolution. It will be by showing themselves to be big enough for the moment, credible leaders of a party and country in a downward spiral of hate and violence.

If Biden does falter, raising doubts about his electability, then perhaps voters look to alternatives, and when they do, they are unlikely to seek out someone who has gone negative on fellow Democrats (a disfavored tactic in a party anxious to crush Trump). They are quite likely to look for a better version of Biden — optimistic, decent, ready to build on the Obama legacy, capable of throwing a knockout punch at Trump and avoiding playing into the cliché of an open-borders socialist. There are any number of candidates who might fit that bill, including those who spoke up so eloquently after the shootings.

After four years of Trump’s meanness and anger — and the resulting political dysfunction and violence — voters are anxious to find a leader who reaffirms the goodness in America and the value of a diverse, tolerant society. As Harris, in one of her most effective stump speech lines has been saying, Trump “does not understand that a sign of strength is not who you beat down and marginalize, it’s who you lift up. This president doesn’t get that — I do.” She has got that right. And so do a bunch of her competitors. Let the best and most electable man or woman win.

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