Former Vice President Joe Biden, presumptive Democratic presidential nominee, left, speaks as Senator Bernie Sanders, an Independent from Vermont, right, listens during a virtual event seen on an Apple Inc. laptop computer in Arlington, Virginia, U.S., on Monday, April 13, 2020.

Sen. Bernie Sanders dropped out of the race for president and endorsed Joe Biden, but he has said he plans to remain on the ballot in order to pick up delegates and have a say at the Democratic National Convention.

Behind the scenes, a group Sanders founded is working to make sure the self-described democratic socialist gets as much influence as possible at the convention, which is slated for August.

Our Revolution, a 501(c)(4) organization that was created in the wake of Sanders' first run for president in 2016, has been pushing its grassroots army to persuade voters to back the Vermont senator in states that have yet to hold their primaries. The goal is to make sure Sanders wins enough delegates to push for key reforms in the Democratic platform.

Paco Fabian, the group's director of campaigns, told CNBC that Our Revolution has activated members in states such as Ohio, New York, Maryland, New Jersey and Pennsylvania. The convention and the primaries have been postponed as the coronavirus forced states to implement social distancing guidelines and lockdowns. Ohio votes April 28, and most of the voting is being conducted through mail-in ballots.

"Ohio is our focus now. Talking about, especially in the moment, the need for Medicare for All, and if we want to have the ability to push the party in that direction, we need as many delegates as possible," Fabian said Wednesday. The group has 20,000 active members in Ohio, and they have been phone banking and texting voters to convince them to back Sanders, even though he's not technically running.

"In the absence of an active Bernie campaign, we are pushing folks to vote for the delegates," he said, noting they need at least 25% of the total delegates in order to have any of their issues considered and possibly added to the party's platform.

Our Revolution's move comes as the Biden campaign has sought to make peace with other liberal and progressive organizations. Many of these groups sent a letter to the former vice president, who is a moderate Democrat, with multiple requests, including not having Wall Street or K-Street leaders be advisors during his general election fight with President Donald Trump.

Our Revolution did not sign that letter, and it's unclear whether it has heard from the Biden campaign, with Fabian declining to say whether those discussions are taking place.

"We are not at liberty to discuss contacts with the Biden campaign at this time," Fabian said.

The Wall Street Journal recently reported that some of the liberal advocacy groups that signed the letter have heard from the Biden campaign and are working to see their demands met.

Biden has tried to appease Sanders supporters in the wake of his endorsement. In a recent Morning Consult poll, most of Sanders' supporters said they would go on and back Biden, but 7% of those surveyed plan to back Trump. Forty percent of Sanders supporters have an unfavorable view of Biden versus just 15% of Democrats.

Biden and Sanders are forming task forces to address issues including the economy, education, climate, criminal justice, immigration reform and health care.

Biden, who also received an endorsement from progressive former rival Sen. Elizabeth Warren, has rolled out a plan that would lower the Medicare eligibility age to 60 from 65, while bolstering his student debt forgiveness plan.

A spokesman for Biden did not respond to a request for comment.