This story — the migrant mass moving north — is the political equivalent of a tropical depression spotted far out into the Atlantic, one that is not much now, but once it hits warm water, could become a dangerous hurricane. Don’t believe me? Check out Tom Edsall’s must-read piece on how new statistical analysis shows that 2016 exit polling was wrong, and the white working class is actually more important to the Democrats than previously thought.

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That migrant mass headed north through Mexico could well be a perfect political storm for the Democrats, who can’t afford to lose the Roseanne vote this fall.

Read the whole thing.