Call your democratic politicians (if you have any) Governor/Senators/House Rep and advocate for pressure for Biden to step down gracefully from the ticket… then prepare to vote for Biden in November because that’s a hell of a longshot.
If you’re talking to people on the fence about voting or not focus more on Biden’s policy achievements instead of Trump being a boogie man. Anyone liberal who is considering sitting out this election has already internally decided that Trump is an acceptable outcome for trying to change the two party system or to avoid dirtying their hands voting for Biden to continue genocide - pushing against people’s fervently held beliefs is a waste of energy… the media really hasn’t put much attention on things that Biden has accomplished so talking those things up won’t make people defensive - you never want to directly challenge someone’s fervently held beliefs because it is extremely difficult to shift those.