They heard the pleas for unity. The dire warnings about a Donald Trump presidency. The tributes to Hillary Clinton as a champion of the downtrodden.
And they were not moved.
Through protests and jeers, a small-but-vocal group of Bernie Sanders supporters have made clear they will never back Clinton for president.
Why the antipathy? Every leading Democrat — including Sanders — backs Clinton. Her political stances aren't drastically different from Sanders' ideas. And she's the only person who can prevent a Trump victory.
The answer has to do with a deep mistrust of Clinton and anger at a primary process they see as rigged. Here's a look at what's driving these forces and whether they could affect the election:
On their political stances, Clinton and Sanders aren't far apart — at least not compared with their differences with Trump. But when it comes to political personas, the gulf is huge.
Sanders is a self-described revolutionary. Clinton is a product of the establishment as a former first lady, senator and secretary of state.
Sanders has been steadfast in his views for decades, calling himself a democratic socialist, denouncing the disparity in wealth in America, and opposing trade deals. Clinton's views have shifted over the years, especially on trade, a key campaign issue.
Sanders attacks Wall Street. Clinton received millions for speeches she gave to Wall Street banks and other businesses — and has refused to release transcripts.
Sanders supporters see Clinton as too hawkish on national security. And they recall with little affection the presidency of her husband, Bill Clinton — in particular his welfare overhaul and tough-on-crime policies.
DISTRUSTING THE PROCESS
Hillary Clinton handily won the Democratic primary, but Sanders supporters say that's because the system was rigged.
Clinton benefited from the overwhelming support of "superdelegates" — party leaders and elected officials who can vote for anyone they choose. And Sanders supporters believe he lost votes because of rules that allow only registered Democrats to vote in many state contests.
Moreover, Sanders supporters were convinced that the officially neutral Democratic National Committee actually favored Clinton. The recent leak of internal DNC emails only reinforced that view.
Danny Keating, a steelworker from Lowell, Massachusetts, who protested in Philadelphia, said "the two-party system is corrupt. It's becoming more evident by the rigged primaries and everything else."
IF NOT HILLARY, WHO?
The never-Hillary forces have limited options in the November election.
Few Sanders supporters like Trump, whom Democrats have cast as a bullying, dangerous con man.
There's Green Party candidate Jill Stein. But she has no realistic shot of being elected, so that's similar to not voting at all — which is another option.
Greg Gregg, 69, of Salem, Oregon, said he intends to vote for Stein. Citing Eugene V. Debs, who repeatedly ran as a Socialist Party candidate in the last century, Gregg said: "I'd rather vote for what I want and lose than what I don't want and win."
Could these lost votes cost Clinton the election? Probably not. Most Sanders supporters are expected to back her.
Still, in a tight race in a battleground state, every vote matters. Democrats recall 2000 when Al Gore narrowly lost Florida, putting George W. Bush in the White House. Some wonder how history might have been changed if votes cast for Green Party candidate Ralph Nader had instead gone to Gore.
Associated Press writer Dake Kang and Geoff Mulvihill in Philadelphia contributed to this report.