Fox News senior political analyst Brit Hume told "The Story with Martha MacCallum" Tuesday that if Sen. Bernie Sanders, I-Vt., wins the Iowa caucuses and the New Hampshire primary -- the first two contests on the Democrats' nominating calendar -- his rivals for the nomination will be plunged into a breakneck race to emerge as the alternative to the self-proclaimed "democratic socialist."

"Does Joe Biden survive that? Does he remain the key alternative or does someone else emerge?" Hume said. "Does possibly [former New York City Mayor] Mike Bloomberg emerge? He's up ahead now, in national polling averages, he's now ahead of [former South Bend Mayor] Pete Buttigieg. It's only eight percent, but it wasn't very long ago that he wasn't anywhere near that. So, we still have a wide-open, unpredictable race here."

With six days to go before the Iowa caucuses, the Real Clear Politics (RCP) polling average showed Sanders leading former vice president Biden by three percentage points in the Hawkeye State. RCP's New Hampshire polling average showed Sanders leading Biden by eight percentage points.

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Hume added that even if the Democratic establishment avoids the nightmare of a potential Sanders nomination, they still face the problem of how to get his voters to the polls.

"Mainstream Democrats, I don't think, want Bernie Sanders to be their nominee, but they certainly want his voters," Hume said. "And if the way this is handled by them -- if eventually he gets aced out -- if the way this is handled is such that they feel their man was cheated as they felt last time [in 2016], and they don't come out to vote for whoever the nominee is, that's a big problem for Democrats. They need those voters in what is expected to be a close election."