George Stephanopoulos: What to Know About DNC Day 3

The Democratic National Convention has swerved from turmoil to unity. Hillary Clinton made history last night when she became the first woman to secure the presidential nomination of a major U.S. party.

Several prominent speakers will address the convention this evening, including President Barack Obama and former New York City Mayor Michael Bloomberg. ABC News' George Stephanopoulos previews the big night.

Turmoil to Unity

The convention in Philadelphia kicked off with chaos amid the release of internal Democratic National Committee emails by WikiLeaks that appear to show party officials looking for ways to impede Sen. Bernie Sanders politically during the primaries. Sanders supporters were particularly vocal on the opening night, with some even booing the Vermont senator when he said during his speech that Clinton "would make an outstanding president."

Sanders' move to end the roll call vote and nominate Clinton helped bring back a united front Tuesday night.

"This Democratic convention got off to such a bad start here after those hacked [Democratic National Committee] emails, and those angry Bernie Sanders supporters really were letting loose on the convention floor," Stephanopoulos said. "But Democrats are much more unified going into Day Three after three big speeches."

Obama Takes the Stage

The president must further unify his party with a powerful speech for Clinton. The two ran against each other for the Democratic presidential nomination in 2008.

"It's up to President Obama tonight to finish the job," Stephanopoulos said. "He'll talk about how he turned a former rival into a loyal partner."

Obama has already publicly spoken about Clinton and supported her campaign. Earlier this month they made a joint campaign appearance in North Carolina, where he said that no one has ever been "more qualified for this office than Hillary Clinton."

He is expected to address the anger many Americans are feeling over recent officer-involved shootings of black people and to defend the progress he believes he has made as president over the past eight years.

As for whether Obama will mention Clinton's Republican opponent, Stephanopoulos said, "I think he will leave the job of attacking Donald Trump - if he can help himself - to Tim Kaine, his debut on the national stage tonight."

The nation will have an opportunity to learn a bit more about the Virginia senator and why Clinton chose him as her vice presidential pick.

Ask Donald Trump Anything

While the Democrats in Philadelphia are awaiting those speeches, Trump will be doing an Ask Me Anything event on Reddit at 6:30 p.m. Eastern time and is expected to begin answering users' questions at 7 p.m., according to a press release.

"I'm going to be watching to see how Donald trump handles this Ask Me Anything question and answer session today. That should be fun watching," Stephanopoulos said.