The Left's position is actually quite fragile. The ethno-nats like to focus on things like 93% of black votes or 73% of Hispanic votes are democrat. But what they don't tell you is how that makes up an enormous swath of their actual voting block.

If black support for Democrats were to fall by 10%, they are guaranteed to lose the election. If it falls all the way to 73% support, they lose every election.

One of the reason the Left lost in 2016 is because millions of voters, somewhere closer to 10 million voted 3rd party rather than Clinton. One of the reasons they "won" in 2020 is because they basically dragged everyone back into voting Biden. They gained back 10 million 3rd party voters, while the Republicans just gained 10 million more voters from the woodwork. Antifa voted Biden, simple as. They can lie all they want, but they absolutely did.

Blue enclaves like SF, LA, CHI, NYC, etc, are lost causes,but their respective states are not.

To a degree. The only reason Republicans can't win illinois is only because of Chicago and Detroit. The rest of the state is blood red. This is the problem everywhere. A Democratic Hive City forces everyone else to succumb to it's will based on population. This means you don't need to corrupt tens of thousands of Boards of Elections. You only need to corrupt less than a dozen.

The reason Florida didn't go blue, and didn't have any voting problems, is because the Boward County Board of Elections was basically drummed out years earlier.