Bernie on motivating Democratic voters

He acknowledges that abortion is a critical issue. But Dems must also address economic issues with the same tenacity if they want to win. And no one does that better than Bernie. Not only do we have to promote the values and policies that will help the working class, we also have to show how the Republicans are fighting every single one of those proposals. And to date I have not seen many if any Dem candidates take him up on doing this. Why?