But it appears that by focusing on so many datapoints and thinking about key demographics, Mr Penn neglected the big fact that primaries are not the same as general elections.

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"If Ross leaves, and some of his key people leave, then you've got a big problem, " Mr. Weiner says.

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Young voters played a big role in Mr. Obama's victory in some key states in 2008, but they don't seem as fired up this year.

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