WI-PPP: Sanders leads Clinton by 6, Cruz and Trump virtually tied.

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This poll has Sanders winning African Americans 51-40.

[Gass3268]

Clinton is ahead with Democrats 50-42.
If she wins by such a comfortable margin in lily white Wisconsin then I doubt that she wins them in her home state by only 12. 

There's a caveat: Closed primaries encourage independents to register as Democrats or Republicans, which would potentially make New York Democrats more favorable to Sanders than they otherwise would be.

Still, its pretty clear that closed primaries favor Clinton regardless, but its probably not as much as exit polling showing Clinton dominating with Democrats would suggest.

Exactly, if you are an independent in a closed primary state you are going to have to pick the party that you at least somewhat align with if you want to participate. Totally different from states that don't have any party registration like Wisconsin.