It was changes by Democrats that made Ohio a GOP state

 Salena Zito:

Where'd you go, Ohio? How a swing state went red

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 The voters had not changed. The Democratic Party most certainly had. The Republican Party changed, too, as it inherited so many of those disaffected conservative Democrats, many of whom had voted for former President Barack Obama twice.

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Paul Sracic, a Youngstown State University political science professor, says that because the Democrats were shedding their voters in favor of an ascendant coalition of young people, minorities, cultural elites, and women, they missed how much that subtraction was affecting the Republican electorate. “And the change has been stunning,” he said.

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There is much more.

 I think as the Democrats moved left, they left behind most of their conservative core.