Constitutional law professor Jonathan Turley said Monday that Democrats' "obsession" with President Trump is eroding what used to define their party.

In a recent op-ed, Turley wrote that Trump has led Democrats to abandon their "core unifying values."

"Trump is remaking the party in his inverse image," Turley wrote.

He said on "Fox & Friends" that Democrats' "all-consuming effort" with opposing Trump is becoming their identity.

"What happens when Donald Trump leaves office? What is left of your party?" he asked.

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Turley noted that when Trump said he wanted troops out of Syria and Afghanistan, Democrats, who have opposed continual wars, called the move "hasty."

"What is left of the Democratic Party beyond being opposed to Donald Trump?" he said Monday.

Turley also had a warning for Republicans, saying that they need to be careful.

"If they just simply become the party of Donald Trump, they're going to have the same vacuum once he leaves the office," he said.

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