As Hillary Clinton, Bernie Sanders, and John Kasich - three people with major ideological and personal differences between them - all made clear in their earlier speeches, the case against Trump is not about policy. The urgency that has united socialists, liberals, and conservatives featured this week is about something much more fundamental, something that is frankly difficult for political reporters who are used to litigating policy and political disputes between the two parties to convey in a way that seems unbiased.

Obama accused Trump of failing to "discover some reverence for the democracy that had been placed in his care." He essentially accused him of corruption and abuse of power, saying Trump had "no interest in using the awesome power of his office to help anyone but himself and his friends." And he accused his successor of a dangerous form of narcissism when he said that Trump had "no interest in treating the presidency as anything but one more reality show that he can use to get the attention he craves."

Obama then detoured to a positive case for Biden. But after some personal reflections on his capacity for empathy and how Biden made him a better president, Obama's case for Biden (and Kamala Harris) became a case against Trump. Biden and Harris "actually care about every American" and they "care deeply about this democracy," and that "the right to vote is sacred," and "that no one including the president is above the law and that no public official, including the president, should use their office to enrich themselves or their supporters."

There was more. Biden would never "use the men and women of our military who are willing to risk everything to protect our nation as political props to deploy against peaceful protesters on our own soil." He and Harris believe "political opponents aren't un-American just because they disagree with you" and that "a free press isn't the enemy." They wouldn't attack the pandemic by "just making stuff up."

But, again, the main point - the reason that a former president who wanted to enjoy a cushier post-presidency of intellectual pursuits (starting with his memoir), international do-goodism, and hobnobbing on yachts with the likes of David Geffen broke the tradition of not pillorying his successor - is the certainty that Trump is doing nothing less than undermining the American system. "That's what's at stake right now," he said. "Our democracy." If the point wasn't clear, Obama gave his speech in Philadelphia before a blown-up picture of the Constitution.

"None of this should be controversial," Obama said, with the characteristic exasperation he exhibits when he can't believe that others don't see something that is so blindingly obvious to him. "These shouldn't be Republican principles or Democratic principles. They are American principles. But at this moment, this president and those who enable him have shown they don't believe in these things."

Of course, that's the big obstacle the Biden convention faces this week: the blinding obviousness of the Trump threat as Democrats see it is not shared by roughly half the country and 90 percent of Republican officeholders. Not only is it not shared by them, but it is passionately denied. The president himself has invented an entire counter-narrative that Obama is a criminal - guilty of "treason" - who masterminded a fraudulent Russia investigation to kneecap his administration from its earliest days.

In a previous era, Obama would have spent some time trying to talk to those on the other side who believed such things. But it's no longer 2004, when Obama became famous for arguing that the blue/red divide was a fiction invented by pundits. "I know that in times as polarized as these, most of you have already made up your mind," he conceded.

His pitch was to those on the fence, Americans "still not sure which candidate you will vote for or whether you will vote at all." He tried to empathize with these Americans and cast them as essentially people who have given up on democracy: a white factory worker with stagnant wages, a Black mom who believes the government "never looked out for her at all," a new immigrant who wonders "whether there is still a place for him here," and a cynical young person turned off from politics because of "the circus of it all, the meanness and the lies and conspiracy theories." His point was that democracy can't be taken away, but it can be given away when enough voters are encouraged to opt out of the system.

Before he was a U.S. senator from Illinois, Obama was a lecturer in constitutional law at the University of Chicago. His view of American history is that the Constitution was an imperfect document that excluded most Americans from citizenship and yet still gave future generations the best system to fix the original document's deficiencies, and that progress is the story of our country.

He closed by retelling that history - the fights for abolition, and labor rights, and religious equality - and reminding voters that however bad things seem now, there is always the chance for renewal.

"If anyone had a right to believe that this democracy did not work and could not work, it was those Americans, our ancestors," Obama said. "They were on the receiving end of a democracy that had fallen short all their lives. They knew how far the daily reality of America strayed from them then. And, yet, instead of giving up, they joined together and they said somehow, some way we are going to make this work. We are going to bring those words in our founding documents to life."

In most Obama speeches that tell the story of American progress and how we have always worked to live up to the promise of our founding documents, he seems optimistic and confident that that history will continue. In Wednesday's speech the question of whether America will get this right this time - at least in his view - seemed uncertain.

This is the same uncertainty Obama has been wrestling with since Trump was elected. According to one of his adviser's memoirs, in late 2016 Obama's confidence in his understanding of the American mood was shaken by Trump's victory.

Since then, Democrats have regained a lot of political turf, mostly in 2018. But after Trump's victory, Obama turned to his aides and asked a question that still hangs over the 2020 campaign.

"What," he wondered, "if we were wrong?"

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