"Either the Democrats are comfortably winning"
Don't get comfortable in a democracy that works.
people get to vote who they want to vote for.
"The alternative is that..." - the illusion of only two choices comes from your having grown up with a broken democracy.
"In which case the whole "turn up and the Democrats will move left" theory is nonsense."
this is nonense.
none of this is the neat logic game you want it to be.
in an election, people get to vote for who they want to vote for.
in this election, Harris is the clear better choice for people who are not selfish.
this does not mean that she wins.