maybe instead of demanding the votes of the left you should earn them. Of course, this only really applies in systems where 2 parties dominate while other parties aren't really a credible option for most people, like the US, which in itself is a systemic flaw that should be addressed if you want a healthy democracy.
You don't get to blame people for not voting your candidate because "it was less bad than the other", if your whole point is being less bad than the other, rather than actually being good, then you're already losing and you should start looking at how to fix this issue before it gets worse. When turnout is lower than usual, like in 2016 in the US but also other elections like Italy in 2022, it means that democracy isn't healthy and there's a systemic problem which is leading to voters getting disillusioned, disengaged and disenfranchised from politics, which is extremely bad and should signal to you that "There's an issue! We need to fix it!" not that "Voters are so lazy/dumb/scum for not getting off their couch and voting [for me]".
Finally, I'd like to reiterate that if you keep asking leftists to vote for you at every election (to beat the other bad guys), yet every time you move further away from the left and/or disappoint leftists, eventually leftists will stop believing your bullshit and not vote you anymore, and you deserve that.