How did pollsters get Bernie Sanders prediction so wrong?

Bernie Sanders' big primary win in Michigan over Hillary Clinton came as a surprise. With the polls predicting a Clinton victory, even some of Sanders' supporters were shocked that he walked away with the majority of the vote. Wednesday morning, with 99.38 percent of polls reporting, Hillary Clinton came out about 20,000 votes under Sanders. Take a look at the final numbers here on our election results page.

So, how did Sanders' narrow upset happen? Voter turnout played a big role.

More than 2.4 million people showed up to vote Tuesday, shattering a primary record from 1972 of just 1.9 million people. In fact, voter turnout was so high that some precincts ran out of ballots

Coincidentally, Bernie Sanders said just a few days ago, "If the voter turnout in Michigan is high, I will win the state of Michigan."

Even our FOX 2 Mitchell poll predicted Sanders needed a miracle to win the primary, and that Hillary would take home more than 60 percent of the votes. We talked to the man himself, Steve Mitchell, of Mitchell Research and Communications, about what happened.

"No one predicted this," he says. "And only did we not get it right, no one was less than double digits for Hillary Clinton." He says the average of the polls had Hillary winning by 21.4 percent.

"I think this changes it dramatically. This is coming into a major industrial state where Hillary Clinton had a strong network in place, where there is a quarter of the voters that are African American that should've been much more strongly in support of Hillary; they weren't. She only won that vote by a 2:1 margin, according to exit polls. I think this changes it dramatically," he continued.

Clinton rode that continued wave of support from black voters in Southern states, though, to claim victory in Mississippi, who also held their primary Tuesday. They accounted for about seven in 10 Democratic voters in Mississippi, and nearly nine in 10 of them supported her.

Congresswoman Debbie Dingell also joins us on FOX 2 to talk about Sanders' win. She has always thought this race was much tighter than the polling suggested.

"Polling is not voting. Polling drives momentum; it drives how people think. We wouldn't be having this same conversation if we just were looking at the vote yesterday, but it's such a dramatic thing because all these polls were showing her 25, 27 points up, which, quite frankly, I never believed," Dingell says.

She says, when looking at the polls, we need to be more objective about them.

"Who are they reaching? How were they reaching young people on cell phones?" she asks. "Polling is just a snapshot of a moment in time, but you really also have to know what their demographics are, how they're reaching people, how they're adjusting it for different things."

You can hear more of her opinion on the polls by watching her interview the video player above. 

Exit polls in Michigan, according to the Associated Press, showed that Sanders' populist theme struck a chord, as more than eight in 10 Michigan Democrats said the U.S. economic system generally favors the wealthy, and just over half of those voters backed the Vermont senator. Nearly four in 10 said they were very worried about the direction of the economy in the next few years, and six in 10 of those favored Sanders.

"Bernie Sanders raised $40 million after he lost South Carolina by 50 points. I can't imagine what's going to happen when he wins a major industrial state."

Sanders and Clinton will face off again tonight at a debate at Miami Dade College in battleground Florida, whose winner-take-all primary is March 15. The candidates will also be speaking to a much wider audience of voters in the delegate-rich states of Missouri, Illinois, Ohio and North Carolina, which are hosting Democratic contests on March 15.

Republican nominee front-runner Donald Trump won in Michigan last night, as expected. You can read more about that here.

The Associated Press contributed to this report.