WATCH: Bernie Sanders gets booed again – but this time he crushes hecklers with the perfect response
Sen. Bernie Sanders speaking at the Democratic National Convention -- ABC screen grab

Sen. Bernie Sanders made an impassioned plea for his voters to get behind Hillary Clinton this fall, but it seems that there are still some holdouts.

While addressing a California delegate breakfast on Tuesday morning, Sanders again told his followers that it was important to elect Hillary Clinton over Donald Trump this fall.

When Sanders gave delegates this message on Monday, he was greeted by a round of boos. This time, however, he was greeted by a mix of boos and cheers.

Undeterred by the mixed reaction, Sanders doggedly stayed on message.

"It is easy to boo, but it is harder to look your kids in the face if we are living under a Trump presidency," the senator told the crowd. "Politics is not easy stuff. You don't get everything you want tomorrow -- ask the people who fought in the civil rights movement."

Sanders's campaign was based on the idea that we need a political revolution that will get people more involved in their government and will make elected officials less reliant on big donors to fund campaigns.

Given this, it's been hard for some Sanders supporters to accept the nitty-gritty realities of politics that Sanders has preached since he endorsed Hillary Clinton. Nonetheless, Sanders will likely keep making his case for electing Clinton from now all the way until November.

Check out a video of Sanders addressing supporters below.