As a leftist, it's important to accept that the Dems will never, ever, ever move to the left unless there's massive grassroots organization such as Unionization and Socialists winning local elections.
People who abstain from voting as protest, however, still think ironically that voting is anything other than loss prevention. If everyone sits out and protests, literally everyone on the Dem side and Trump wins in a landslide, and Trump manages to keep elections for 2028, the Dems still won't move to the left.
That's why voting as a leftist is about loss prevention, rather than gaining material change. The movement leftward comes from upsetting the entire 2 party process by flipping the table itself. Mass Unionization and taking of key seats is exactly how you (non-violently) upset the process and force concessions or enable third party to be theoretically viable.
Until then, however, any leftist not voting Dem in the federal election is sorely misguided.
When the left sits out, the right wins. And when voters sit out, parties leave them behind. Political parties will chase likely voters every single time, and if you're not a voter, your opinion doesn't even register to the leaders of this country. How even could it, if you don't participate?!