Karl Rove breaks down how the Democrats' Iowa caucus will be won

The Iowa Democratic presidential caucus will be won based on the decisions made by the supporters of lower-tier candidates, former White House deputy chief of staff Karl Rove said Tuesday.

Appearing on "America's Newsroom" with host Bill Hemmer, the Fox News contributor said that any preliminary poll numbers are just that — preliminary.

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A Monmouth University poll released Tuesday shows former Vice President Joe Biden topping Vermont Sen. Bernie Sanders, Indiana Mayor Pete Buttigieg, and Massachusetts Sen. Elizabeth Warren in the Iowa Democratic caucuses. Biden is shown at 24 percent, compared to 19 percent in November. Sanders is at 18 percent, Buttigieg at 17 percent, and Warren at 15 percent.

However, a Des Moines Register/CNN poll from Monday puts Sanders at the forefront with 20 percent, Warren with 17 percent, Buttigieg with 16 percent, and Biden trailing with only 15 percent.

"There's only one significant difference in the poll," said Rove, noting that most percentages in the two polls were relatively close.

"The only one is 24 or 18 for Biden. Which one is it? And, a lot hangs on that because 24 gives him a pretty convincing first-place finish in a state where he's not been doing all that well."

Rove told Hemmer that 18 percent puts Biden "basically in a four-way tie" for first-place and each candidate would get roughly the same number of delegates. Caucusgoers who support a candidate receiving less than 15 percent in a precinct are asked to support a second-choice candidate that remains above the threshold.

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"Where Sen. Amy] Klobuchar and [Andrew] Yang and [now former candidate Cory] Booker...Tom Steyer and [Rep.] Tulsi supporters go to could a) determine who the winner is and b) could determine who gets more delegates than they otherwise would get given their poll numbers today," Rove stated.