How Bernie Sanders snatched the biggest upset of the campaign over Hillary Clinton

Despite public polls that showed him losing by more than 20 points to former Secretary of State Hillary Clinton, Sen. Bernie Sanders pulled off a narrow, crucial upset victory in Michigan's primary Tuesday.

Exit polls from the state gave a peek behind the motivations of voters who helped deliver Sanders the stunning victory.

According to CNN exit polls, Clinton cleaned up among self-identified Democrats, who made up almost 70% of exit-poll respondents.

But self-identified independents - who made up 28% of poll respondents - overwhelmingly sided with Sanders. Seventy-one percent broke for Sanders, while only 28% broke for Clinton.

Sanders also prevailed among liberal voters, who made up the majority of the exit-poll respondents. Fifty-four percent of self-identified liberals sided with Sanders, while the smaller group of self-identified moderate Democratic primary voters cast their ballots for Clinton.

Clinton maintained her high level of support among black voters in Mississippi, where she prevailed over Sanders on Tuesday night in a dominating victory. Importantly Sanders was able to close that gap a bit in Michigan, picking up 30% of the black vote to Clinton's 65%. The former secretary of state lost by almost 30% among white men, who made up a significant chunk of the electorate.

Sanders' economic-policy platform also appeared to resonate with Michigan Democratic voters.

Of the issues raised by exit pollsters, income inequality was the second-most important issue dictating how voters chose to cast their ballots. Of the 27% of voters who said income inequality was their No. 1 concern, Sanders beat Clinton by more than 20 points.

Clinton's campaign was quick to caveat the results, pointing out that Clinton's blowout win in Mississippi and narrow loss in Michigan meant that she would actually build on her already sizeable delegate lead Tuesday night.

But Sanders' win demonstrated that Clinton still has a tough fight to the nomination, as delegate-heavy states like Ohio and Wisconsin - which resemble Michigan demographically - provide openings for Sanders to potentially eat at Clinton's delegate lead.