Video: Trump Mocks Obama’s Speech at DNC: ‘The Reason I’m Here is Because of President Obama and Joe Biden.’

Here's a transcript of part of Obama's speech from CNN.

Good evening, everybody. As you've seen by now, this isn't a normal convention. It's not a normal time. So tonight, I want to talk as plainly as I can about the stakes in this election. Because what we do these next 76 days will echo through generations to come.

I'm in Philadelphia, where our Constitution was drafted and signed. It wasn't a perfect document. It allowed for the inhumanity of slavery and failed to guarantee women -- and even men who didn't own property -- the right to participate in the political process. But embedded in this document was a North Star that would guide future generations; a system of representative government -- a democracy -- through which we could better realize our highest ideals. Through civil war and bitter struggles, we improved this Constitution to include the voices of those who'd once been left out. And gradually, we made this country more just, more equal, and more free.

The one Constitutional office elected by all of the people is the presidency. So at minimum, we should expect a president to feel a sense of responsibility for the safety and welfare of all 330 million of us -- regardless of what we look like, how we worship, who we love, how much money we have -- or who we voted for.

But we should also expect a president to be the custodian of this democracy. We should expect that regardless of ego, ambition, or political beliefs, the president will preserve, protect, and defend the freedoms and ideals that so many Americans marched for and went to jail for; fought for and died for.

I have sat in the Oval Office with both of the men who are running for president. I never expected that my successor would embrace my vision or continue my policies. I did hope, for the sake of our country, that Donald Trump might show some interest in taking the job seriously; that he might come to feel the weight of the office and discover some reverence for the democracy that had been placed in his care.

But he never did. For close to four years now, he's shown no interest in putting in the work; no interest in finding common ground; no interest in using the awesome power of his office to help anyone but himself and his friends; no interest in treating the presidency as anything but one more reality show that he can use to get the attention he craves.

Donald Trump hasn't grown into the job because he can't. And the consequences of that failure are severe. 170,000 Americans dead. Millions of jobs gone while those at the top take in more than ever. Our worst impulses unleashed, our proud reputation around the world badly diminished, and our democratic institutions threatened like never before.

Now, I know that in times as polarized as these, most of you have already made up your mind. But maybe you're still not sure which candidate you'll vote for -- or whether you'll vote at all. Maybe you're tired of the direction we're headed, but you can't see a better path yet, or you just don't know enough about the person who wants to lead us there.