First Read is a morning briefing from Meet the Press and the NBC Political Unit on the day's most important political stories and why they matter.

Bernie’s Big Night

PHILADELPHIA – After Republicans’ messy convention last week, Democrats experienced their own chaos even before the convention started here -- with the announcement that DNC Chair Debbie Wasserman Schultz would step down as a result of the WikiLeaks email dump. The controversy only elevates tonight’s convention speech by Bernie Sanders, who was the target of a handful of the leaked DNC emails, including one questioning his religious faith. Sanders gladly accepted the resignation (which will take place once the convention ends). “Debbie Wasserman Schultz has made the right decision for the future of the Democratic Party. While she deserves thanks for her years of service, the party now needs new leadership that will open the doors of the party and welcome in working people and young people,” he said in a statement. While Sanders isn’t expected to pull a Ted Cruz -- he’s already endorsed Clinton and said on “Meet the Press” yesterday that he remains in Clinton’s corner even after the leaked emails -- his speech will set the tone for the rest of the convention. Sunday’s news wasn’t a great way to kick things off in Philly for Democrats, and they can’t afford to have the controversy spill over into the next four days. That’s why all eyes will be on Sanders, who closes out the first night of speeches.

Can Sanders convince his supporters to get on the Clinton Train

You could argue that Wasserman Schultz’s resignation is maybe the most unifying single event that’s happened so far in the Democratic race. (Indeed, on MSNBC yesterday, Sanders supporter Ben Jealous told host Tamron Hall that he was endorsing Clinton after the DWS news.) But we don’t know yet how Sanders delegates -- and young progressives -- will respond. That’s why Sanders’ speech has some extra drama to it that didn’t exist earlier.

Day One’s schedule

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The first day of the Democratic convention is entitled “United Together,” and the focus will be on Hillary Clinton’s “lifelong work and commitment to putting families first,” the Clinton campaign says. The featured speakers, starting in the 9:00 pm ET hour, include (in order) New Jersey Sen. Cory Booker, First Lady Michelle Obama, keynote speaker Elizabeth Warren, and Sanders. Also speaking will be DREAMer Astrid Silva.

Trump gets a bump. (Or does he?)

The stakes for Democrats having a successful convention are now greater with the news that Donald Trump got a bounce from Cleveland. A new CNN poll shows him now leading Hillary Clinton by three points, 48%-45%. Clinton was ahead in CNN’s previous poll, 49%-42%. In a four-way race in the new poll, it’s Trump 44%, Clinton 39%, Gary Johnson 9%, and Jill Stein 3%. But while the CNN poll shows a bump for Trump, a new CBS poll finds that the contest remains tied, 42%-42%. Remember, the truest apples-to-apples comparison of the state of the presidential race will be polling conducted AFTER the Dem VP rollout and convention. But it’s clear from most of the polling we’ve seen (in addition to the CNN and CBS polls) that Trump got a bounce out of Cleveland, either big or small. And the reason shouldn’t be surprising: He had a lot of room to grow, especially with Republican voters.

Democrats had already lost confidence in Wasserman Schultz before the WikiLeaks leak

Going back to Debbie Wasserman Schultz’s resignation, NBC’s Alex Seitz-Wald has more on the story. “[S]tarting even before [the WikiLeaks leak], many Democrats had privately lost confidence in her leadership. ‘She's essentially a pariah in every corner of the party,’ said one veteran Democratic strategist, who spoke on condition of anonymity to discuss internal politics. ‘This has needed to happen for a long time.’ For instance in late May, after a news report that Democrats were considering ousting Wasserman Schultz, Senate Democratic Leader Harry Reid called her to say he would not put out a statement defending her. Wasserman Schultz also overrode the White House and the Clinton campaign in her choice of communications director for the DNC last fall. The key role went vacant for five months as the various parties tried to find a candidate acceptable to her, with some allies criticizing the process and outcome.”

NYT: Researchers have concluded that DNC was breached by two Russian intelligence agencies

But there’s another important angle to the WikiLeaks leak: Russia’s alleged involvement. The New York Times: “Until Friday, that charge, with its eerie suggestion of a Kremlin conspiracy to aid Donald J. Trump, has been only whispered. But the release on Friday of some 20,000 stolen emails from the Democratic National Committee’s computer servers, many of them embarrassing to Democratic leaders, has intensified discussion of the role of Russian intelligence agencies in disrupting the 2016 campaign... Proving the source of a cyberattack is notoriously difficult. But researchers have concluded that the national committee was breached by two Russian intelligence agencies, which were the same attackers behind previous Russian cyberoperations at the White House, the State Department and the Joint Chiefs of Staff last year. And metadata from the released emails suggests that the documents passed through Russian computers. Though a hacker claimed responsibility for giving the emails to WikiLeaks, the same agencies are the prime suspects. Whether the thefts were ordered by Mr. Putin, or just carried out by apparatchiks who thought they might please him, is anyone’s guess.”

It’s Hillary’s convention, but Obama might be the most important factor

There’s so much attention today on Bernie Sanders, Debbie Wasserman Schultz, and of course Hillary Clinton. But maybe the biggest player this week -- and over the next 100 days -- is President Obama, who addresses the convention on Wednesday. As one of us writes, “This Democratic convention is Hillary Clinton's party. But the person who's hovering over it — and still shaping the overall Democratic Party's policies, tone and temperament — is the man speaking Wednesday night: President Barack Obama. Indeed, Obama could very well be the most important figure in the presidential contest between now and Election Day, whether it's galvanizing Clinton's supporters or motivating Donald Trump's. Obama's job-approval rating stands at 51 percent in the latest NBC News/Wall Street Journal — the third-straight NBC/WSJ survey where his approval has been above 50 percent. What's more, nearly half of American voters (49 percent) give the president credit for what they say is the country's improving economy. ‘Those are powerful assets for the Clinton campaign,’ said Fred Yang, a Democratic pollster who co-conducts the NBC/WSJ survey with Republican pollster Bill McInturff.”

The Team of Resumes vs. The Outsider

As for Hillary Clinton tapping Tim Kaine to be her running mate, it’s worth noting how this move doubles down on experience, given Kaine’s resume (mayor, governor, party chair, senator). So it’s the Team of Resumes vs. The Outsider.

On the trail

Hillary Clinton, in Charlotte, speaks to the Veterans of Foreign War convention before stumping in the city at 12:30 pm ET… Donald Trump and Mike Pence campaign at a town hall in Roanoke, VA at 3:30 pm ET, and then hold a rally in Winston-Salem, NC at 8:00 pm ET.