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Sen. Mitt Romney, one of the most vocal Republican critics of President Donald Trump, said Sunday he's not ready to endorse Trump for re-election.

On CNN's State of the Union, Romney said it's "way too early" to throw his support behind President Donald Trump's re-election bid.

In 2016, Romney cast his presidential ballot for his wife, Ann. He said he may do so again.

"We'll have to wait to see how she does," he said.

Watch the clip below via CNN.