That alone is bad news for Barack Obama, at a time when blue collar and union support has fallen significantly enough from 2008 levels to cause a wave of worry.

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Hillary Clinton's support among blue-collar voters here, "We did fear the Obama-Clinton ticket, " Cowan tells CNN.

CNN: Despite political climate, Michigan could go either way

Exit polls after previous primaries show Obama is cutting into Clinton's base by gaining support among blue-collar workers and Latino voters.

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