Former House Speaker Nancy did not mention Trump by name during her speech, including when addressing Jan. 6.

"Never before had a president of the United States so brazenly assaulted the bedrock of our democracy, so gleefully embraced political violence, so willfully betrayed his oath of office," she said.

"Let us not forget who assaulted democracy on Jan. 6. He did! But let us not forget who saved democracy that day. We did."

She said lawmakers returning to the Capitol that same night demonstrated that "American democracy prevailed" and called on voters now to "reject autocracy" and "choose democracy" by electing Harris and Walz.

After a warm welcome from the crowd, former House Speaker Nancy Pelosi began her remarks thanking Biden for his "patriotic vision of a fairer America."

"Millions of jobs. Stronger infrastructure. A Biden child tax credit. Rescuing union pensions. Honoring our veterans. Bold climate action. Lowering the costs of prescription drugs," she said of the presidency's accomplishments, calling it one of the most successful of modern times.

Pelosi said Harris is now "ready to take us to new heights."

"Officially, she is a leader of strength, with wisdom and eloquence on policy -- most recently demonstrated fighting for women’s right to choose. Politically, she is astute and strategic in winning difficult elections -- quickly securing the nomination with dignity and grace and choosing Tim Walz as our vice president," Pelosi said.

Former House Speaker Nancy Pelosi is addressing the DNC after appearing to play a significant role in Biden's exit from the top of the Democratic ticket.

Pelosi, who last month endorsed Harris to be the party's nominee for president, did not publicly call on Biden to withdraw from the race. Instead, Pelosi, in a July 10 interview, declined to directly answer when asked if Biden had her support in his reelection bid after his ruinous debate performance.

At the time, Biden had already committed to running for reelection, writing in a statement congressional Democrats days earlier that he was "firmly committed" to staying in the race.

Her comments blunted any progress Biden was trying to make persuading congressional Democrats that he was up for the job. And Pelosi's ambiguous public comments instead created space for rank-and-file Democrats to pressure the president to drop out.

-ABC News' Sarah Beth Hensley, John Parkinson, Lauren Peller and Allison Pecorin

Bill Clinton, like many of this week's keynote speakers, is advising Democrats at the United Center and around the country not to get distracted or overconfident this election cycle.

Seemingly referencing the 2016 election, he said: "We've seen more than one election slip away from us when we thought it couldn't happen. When people got distracted by phony issues.

"This is a brutal, tough business. I want you to be happy," he continued.

"One of the reasons that Vice President Harris is doing so well is that we're all so happy. But you should never underestimate your adversary."