Yep, there's no doubt that the Republicans have stoked this hyperpartisanship, because they have the mechanisms of the electorate in their pocket (Electoral College, the vast majority of gerrymandered districts), so they can win elections with a minority of the votes.

Given that the vast majority of those on the real left (as opposed to what many Americans call the left, which is actually the centre) only vote Democrat because there is no true left-leaning party, it may well be that the Democrats have to disappear or properly re-invent themselves. Republican-lite is nop longer a viable political strategy (and really hasn't been for a long time).