Will this make New York more or less left wing? I'm actually curious.
Otherwise you get a pyramid of control that drives towards extremes.
Historically, let's say dems = 51% of voters, everyone votes party line.
Dems have a primary, and someone (usually pretty far left) motivates base and gets 30% of primary vote and wins primary with most votes.
Let's assume a 10% of dem's vote in primaries.
So you have 10% * 50% * 30% = 1.5% of voters voting for the primary winner.
They then go onto a matchup in general, but because it's a dem district, they win there as well (republicans usually also pick someone further right).
So 1.5% of more extreme / activist voters end up really deciding, because by the time you get to general there is no more competition.