Democratic presidential candidate Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE's campaign is raising money to help send his delegates to Philadelphia next month for the Democratic National Convention.

In an email Tuesday, the Vermont senator's campaign encouraged supporters to donate $2.70 before Thursday's midnight Federal Election Commission deadline to help get the campaign's nearly 1,900 delegates to the convention. It can cost more than $4,000 per delegate, the campaign said.

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"Our delegates are not wealthy campaign contributors. They're not party insiders or establishment elites. They're working folks, and it's not easy for many of them to fly to Philly and stay in hotels for a week," Sanders campaign manager Jeff Weaver said in the email.

"We really need to have all of our delegates at the Democratic convention because we expect there could be critical votes for the party platform and electoral process. We'd hate to fall short on these votes because some of our delegates couldn't afford to go to the convention."

Weaver said hotels are booked months in advance and then sold at higher prices, adding that lobbyists plan "all sorts of fancy parties." The political establishment can easily navigate it, he said.

"Our political revolution is not made up of people like that," he continued. "Our folks need help to get to the convention and stay there."

Sanders has remained in the race to continue to fight for his progressive ideas. This past weekend, he called on presumptive Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE to "stand up" and "be bolder" on policies involving education and healthcare.

He said last week he would vote for Clinton but said he is waiting for her to make major concessions on policy issues, such as on a $15 minimum wage, healthcare and education.