WASHINGTON—Bryan Yarde, a 25-year-old independent voter from Florida who says he leans conservative, is closely following the Republican presidential primary—and doesn’t like what he sees from the two leading candidates, businessman Donald Trump and Texas Sen. Ted Cruz.

“The nativist tendencies of Cruz and Trump are pretty atrocious,” said Mr. Yarde, adding that he would consider supporting Democrat Hillary Clinton if either man wins the GOP nomination.

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