Be an actual opposition party, stop playing nice with Republican politicians. Stop lurching towards the right, stop ignoring your minority, young and progressive base. Focus harder on class solidarity, stop letting rich old white people and their donors/advisors call the shots. Excite your fucking base and make them want to rush to the polls to vote for your candidate, not just "well, he's better than the Republican." Stop playing defense on the socialist attacking, just keep pressing on and ignore it, it legitimizes the attacks.
So basically nothing that needs to happen will happen.