Sanders needs to win all the remaining contests by a 20-point margin to catch up to Clinton in pledged delegates.

“There’s a pathway to victory for Sen. Sanders, but I think you know it’s certainly gotten brambled,” said Neil Sroka with the progressive group Democracy for America, which supports Sanders.

Hillary Clinton’s lead over Sanders in pledged delegates is more than twice as large as then-Sen. Obama ever had in 2008. Even so, Sroka hopes Sanders will stay in it through the final contests in June, running a spirited campaign.

“There is not a single doubt in my mind that the strong campaign that Bernie Sanders is waging right now is making the Democratic Party better, stronger and more focused on the populist progressive issues that we need to take on if we are going to be successful in November,” Sroka said.