Voter suppression, coherent message telling voters how their lives will be better, authenticity so they know you mean it, listening to and appealing to all components and regions of the traditional Dem coalition, outreach to new voters, keeping the other side from rigging things like voting machines and voter registration lists and illegal donations and activities and interference like Russia and Comey, and then delivering for your constituencies in order to help the constituencies AND the next candidate who runs. (Thanks, Obama.)