Obama said to build a true Democratic majority, they have to give grace to people who may not align with their political views.

"That sense of mutual respect has to be part of our message," he said. "Our politics have become so polarized these days that all of us across the political spectrum seem so quick to assume the worst in others unless they agree with us on every single issue."

"We start thinking that the only way to win is to scold and shame and out-yell the other side. And after a while, regular folks just tune out or they don’t bother to vote," he continued. "Now that approach may work for the politicians who just want attention and thrive on division, but it won’t work for us to make progress on the things we care about, the things that really affect people’s lives."

Obama later acknowledged those ideas "can feel pretty naive right now" but was adamant "the ties that bind us are still there."

The former president took a moment to note the achievements of his signature policy achievement.

"I notice since it became popular, they don't call it 'Obamacare' anymore," he said, prompting laughter.

Obama went on to say Harris will continue to build on that progress.

"Kamala knows we can't stop there, which is why she'll keep working to limit out-of-pocket costs" he said.

Obama commended Harris for her vice presidential selection.

"Let me tell you something. I love this guy," he said of Minnesota Gov. Tim Walz. "Tim is the kind of person who should be in politics. Born in a small town, served his country, taught kids, coached football, took care of his neighbors. He knows who he is and he knows what's important."

He said the Harris-Walz ticket is the embodiment of America's story.

"A story that says we are all created equal, all of us endowed with certain inalienable rights, that everyone deserves a chance, that even when we don't agree with each other, we can find a way to live with each other," he said. "That's Kamala's vision. That's Tim's vision. That's the Democratic Party's vision."

Obama derided Trump's campaign for trying to pit Americans against one another.

"Donald Trump wants us to think that this country is hopelessly divided between us and them, between the real Americans who of course support him and the outsiders who don't," he said. "And he wants you to think that you'll be richer and safer, if you will just give him the power to put those other people back in their place."

"It is one of the oldest tricks in politics from a guy whose act has, let's face it, gotten pretty stale," he continued. "We do not need four more years a bluster and bumbling and chaos. We have seen that movie before. And we all know that the sequel is usually worse."

"America is ready for a new chapter. America is ready for a better story. We are ready for a President Kamala Harris."

4:13

Barack Obama at the DNC: 'Trump has not stopped whining'

The former president warned against a second Trump presidency, saying, "The sequel is usually worse."