PHILADELPHIA — Nearly eight years after Barack Obama took the oath of office amid a crumbling economy, the president spoke stirringly Wednesday night of a country that had come back from the brink. He threw his full support behind his former secretary of state, Hillary Clinton, as the only candidate capable of continuing the work that he had started to make an already-great America even greater.

“After the worst recession in 80 years, we’ve fought our way back,” Obama told an exuberant crowd at the Democratic National Convention in Philadelphia. “By so many measures, our country is stronger and more prosperous than it was when we started. And through every victory and every setback, I’ve insisted that change is never easy, and never quick; that we wouldn’t meet all of our challenges in one term, or one presidency, or even in one lifetime.”

“I am more optimistic about the future of America than ever before.”

It was a stark acknowledgement that despite the economic recovery, millions of Americans—many of them now supporting the Republican nominee—have been left behind. “Yes, we still have more work to do,” Obama continued, offering a clear-cut different vision for the country than the dark picture painted last week at the Republican National Convention by Donald Trump. “That work involves a big choice this November. Fair to say, this is not your typical election. It’s not just a choice between parties or policies; the usual debates between left and right. This is a more fundamental choice—about who we are as a people, and whether we stay true to this great American experiment in self-government.”

In any other election, Obama’s prime-time endorsement would seem obligatory, but Trump, as Democrats highlighted repeatedly over the course of their quadrennial convention, represents a singular challenge to the legacy of the nation’s first black president. With his calls to build a wall to keep immigrants out, to ban Muslims, to repeal Obamacare, to reverse progress to combat climate change, and to abandon America’s allies, the Republican presidential nominee threatens to undo much of Obama’s vision for the country, potentially setting his progressive agenda back by decades. “What we heard in Cleveland last week wasn’t particularly Republican—and it sure wasn’t conservative,” the president argued. “What we heard was a deeply pessimistic vision of a country where we turn against each other, and turn away from the rest of the world. There were no serious solutions to pressing problems—just the fanning of resentment, and blame, and anger, and hate. That is not the America I know.”

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As Obama spoke, it seemed hard to remember that there was a time when Clinton’s 2016 strategy, too, involved distancing herself from his accomplishments. But as Obama’s popularity has rebounded—even with the Republican-controlled Senate thwarting most of his initiatives in past years—Clinton began to cast herself as the candidate who would continue his legacy, a task made even easier when Trump became the nominee.