> Independents — who are somewhere in the middle This seems factually wrong? Maybe most independents are in between the two parties, but not all. Look at Bernie Sanders for example, I would say he's to the left of the Democratic party. I thought maybe the Gallup poll they are referencing had a weird definition of an independent requiring it to be between the two parties, but I'm not seeing that either.
Aren't independents people who haven't declared any party affiliations? They are usually in the middle, but could have extreme Democrat or Republican views.
Is there any evidence for this, or even definition of this? I'd define it as swing voters who tend to mix up their ballot between the two parties, and I'd be surprised if the percentage of people who did that broke double digits.