Bernie Sanders supporters rally at Democratic National Convention

Supporters of Hillary Clinton's former rival, Vermont Senator Bernie Sanders, converged Sunday in Philadelphia, the site of this week's Democratic National Convention.

Protesters marched through the streets and gathered in Philadelphia's FDR Park.

A supporter of Sanders poses with his effigy at Philadelphia's city hall.

Some dressed in costumes. This man was wearing an eerily lifelike Sanders mask.

Sanders supporters chanted "Hell no, DNC, we won't vote for Hillary" and "This is what democracy looks like."

Though Sanders has endorsed presumptive Democratic nominee Clinton, he also hasn't given up his delegates. 

Sanders has 1,894 delegates (including both pledged and super delegates) to Clinton's 2,807.

Sunday's pro-Sanders rallies were the first of what will likely be many over the course of the convention.

The rallies had been planned for months, but likely surged in popularity due to recent tensions within the party.

Many Sanders supporters believe their candidate is the rightful nominee, beaten only because the Democrats put their weight behind Hillary. This man's partially blocked sign says, "Democrats give rats a bad name."

The protests were spurred on by the Democratic party's recent email scandal.

Emails from party chair Debbie Wasserman Schultz released by WikiLeaks suggest the Democrats showed favoritism toward Clinton during the primary. Wasserman Schultz resigned Sunday evening.

Sanders has said he was "disappointed" but unsurprised by the views expressed by Wasserman Schultz in the leaked emails.

Clinton's vice-presidential pick, announced Saturday, also stirred up tensions among Sanders devotees. 

While there had been rumours that she might pick progressive Senator Elizabeth Warren, she instead chose Senator Tim Kaine, who has been described as a "business-friendly" Democrat. 

Here, a Sanders supporter holds up a doll made in his likeness.

Some Sanders supporters are threatening a 'DemExit.' 

The DemExit group has a list of demands for the DNC, including the elimination of super delegates. If these demands aren't met, they're threatening to organize a mass effort to de-register Democratic voters.

Supporters vow 'Never Hillary.'

Republican presidential nominee Donald Trump has made attempts to woo Sanders voters, receiving backlash from the Vermont senator himself. Whether they're voting for Trump or abstaining altogether, some Sanders supporters have made it clear they refuse to vote for Clinton.

Sanders has been popular among young voters.

The 74-year-old is credited with getting many millennial Democrats to vote in the primaries for the first time.