Supporters of former Democratic presidential candidate Bernie Sanders are making their presence ‒ and unhappiness over him not being the nominee ‒ felt ahead of the Democratic National Convention in Philadelphia, Pennsylvania.

The Democratic Party is trying hard to portray that it is unified, especially after the divisions that were at the forefront of last week's Republican National Convention in Cleveland, Ohio.

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At the California delegation breakfast on Monday morning, Sanders supporters chanted his name and booed any mentions of presumptive Democratic nominee Hillary Clinton.

A raucous morning at California delegates breakfast at DNC. Bernie Sanders supporters booing speakers @FoxNewspic.twitter.com/hrFRIjBGjd — Christine Devine (@DevineNews) July 25, 2016

Texas delegates have been warned not to boo anyone at the convention, or their credentials will be pulled. “You’re not going to embarrass the state of Texas,” they were told, according to Texas Tribune reporter Patrick Svitek.

.@BernieSanders delegates and fans hold up handmade signs for their states. #DemsInPhillypic.twitter.com/ljk9hUhBxd — Danny Freeman (@DannyEFreeman) July 25, 2016

When the Vermont senator spoke to his delegates, boos again rained down at the mention of how the Democratic National Committee handled the primary process.

.@algranell on #Periscope: At DNC with killer mike https://t.co/dOlLWl184j Bernie speaking live — Phoebe Beach (@PhoebeBeach) July 25, 2016

“Make no mistake about it we have made history!” Sanders said. “And as all of you will recall, when we began this campaign over a year ago, we were considered to be fringe players among the establishment and corporate media,” he continued as the audience booed.

.@BernieSanders delegates and fans literally run to get the best seats to see him speak. #DemsInPhillypic.twitter.com/YMh7Z37Mfz — Danny Freeman (@DannyEFreeman) July 25, 2016

“Well, a year has come and gone. we're not fringe players anymore!” he said chants over of “Bernie! Bernie! Bernie!”

‘We want Bernie!’ Sanders delegates boo when told to vote for Clinton & Kaine #DemsInPhillyhttps://t.co/2hEH7M8hBhpic.twitter.com/Pvclisx3kr — RT America (@RT_America) July 25, 2016

Many people protesting outside the convention center are Sanders supporters.

Everywhere you go in philly you see @BernieSanders supporters. They are marching and organizing. #DemsInPhillypic.twitter.com/geYlKuLjcz — KatBrezler (@KatBrezler) July 25, 2016

Some are chanting, "Lock her up!" ‒ a chant popular at the RNC last week.