Donald Trump and Marco Rubio won Tuesday’s night primetime Republican debate, according to an overnight poll of Internet users who watched the contest, but Mr. Trump came out as the favorite among Republicans and left the best impression about his ability to serve as president.

Some 24% of debate-viewers named Mr. Trump and 23% picked Mr. Rubio as the winner of the eight-candidate event, which was sponsored by the Wall Street Journal and Fox Business News. Ted Cruz and Ben Carson followed, with 13% declaring each to have won.

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