Don't Dare Run For President, Senator Tells Oprah

Senator Marco Rubio says despite the fact Oprah is rich and famous, Trump's more famous and he'd beat her in a head-to-head 2020 election.

TMZ got the Republican Senator Monday at Reagan National Airport and he conceded Oprah is loved by millions, but running for President is a whole other Oprah. He says once she starts taking positions, lots of people who liked her are likely to bail.

On the positive side, he seems to think she'd have the inside track for the Democratic nomination. He knows from experience ... running against someone super famous is tough.