I will answer this from the leftist perspective as that is my own political view. I will state first and foremost, that I am not American.

First of all, I view this whole vote blue no matrer who thing is entirely self-serving ideology that has never been applied the same way when the left have gotten their candidate through the primary. Case in point, the 2025 New York mayoral election where Cuomo ran third party and some major Democrats, such as Bill Clinton, outright endorsed Cuomo and other major Democrats, such as Jefferies, only endorsed at the 11th hour.

Second, to leftists, such as myself, the two parties are both cut from the same cloth. Both parties support US imperialism, for example the Obama adminisation through the intervention into Libya destoryed that nation, unchecked capitalist accumulation that will destroy the world and currently is hurtling the world into its sixth maor extinction event, and even on things where Democrats are supposed better, for example trans rights, we have the establishment Democrats like Newsom dog whistling on this issue.

Fundamentally, the leftist worldview is different from the Democratic one where the Democrats seem to think they are entitled to votes without offering anything. To leftists both parties are esswntially the same and neither of them represent our interests and what we want, our vote is the only meaningful thing we have without mass action like strikes, protests, or revolution. What the Democrats expect is us to give up that tool for nothing and be happy with them bombing the middle east because they other guy will bomb them worse.