Democratic presidential candidate Sen. Bernie Sanders (I-Vermont), speaks at the Alliance for Retired Americans 2015 National Legislative Conference in Washington. AP Democratic presidential candidate and Sen. Bernie Sanders (I-Vermont) just admitted what most political strategists already know: He has a minority-voter problem.

In an interview with The New York Times published on Saturday, Sanders admitted that he needs to make major inroads with nonwhite, nonliberal voters in order to overtake presumed Democratic front-runner Hillary Clinton.

"I’m not well known in the African-American community, despite a lifelong record," Sanders told The Times. "That’s a real issue, and I have to deal with it."

Since announcing his presidential bid in April, Sanders has emerged as Clinton's most powerful primary challenger, touting his populist economic message to increasingly large crowds.

The message has clearly resonated with many early primary voters. The self-described "Democratic-socialist" has jumped in the polls — in the early voting states of Iowa and New Hampshire, multiple polls show Clinton's support slightly dipping while Sanders' has surged.

But though the Clinton campaign has been vocal about the threat Sanders poses, the data shows that he does indeed have a demographic problem that will prove difficult to overcome outside those two early states, where Democratic primary voters are overwhelmingly white and liberal.

"If Sanders wins Iowa or New Hampshire, it will build a lot of momentum for him that will help in the states that follow, but he's still going to struggle in places like South Carolina with large black populations and Nevada with large Hispanic populations unless he improves his appeal to nonwhite voters," Tom Jensen, the director of the firm Public Policy Polling, told Business Insider.

Jensen said most recent polls put Clinton's support among African-American voters at around 70% to 80%. And as The Times notes, Sanders remains virtually unknown outside the liberal enclaves where he has campaigned heavily.

Sanders told The Times that he hopes his populist economic message will unite working-class voters, cutting across race, party, and ideology.

“I look at these things more from a class perspective,” Sanders said. “I’m not a liberal. Never have been. I’m a progressive who mostly focuses on the working and middle class.”

Sen. Bernie Sanders (I-Vermont) in Iowa. Reuters/Jim Young

It's unclear if this strategy will pay off for Sanders, but there are some reasons for his campaign to be optimistic: Even if voters don't know Sanders, a big chunk of them are sympathetic to the positions on income inequality that he's espoused for years.

According to a recent Gallup poll, the vast majority of Americans feel that the distribution of wealth in America is unfairly concentrated at the top. The same Gallup poll found that a majority of Americans support raising taxes on the rich and redistributing the money.