Former U.S. Secretary of State Hillary Clinton won victories in four of the five states Tuesday, with large support from black voters in southern states including Florida and North Carolina. But her African-American support was not as strong above the Mason-Dixon line where Clinton won less than 70 percent of the vote among black voters, underscoring a northern-southern divide with a key Democratic constituency.

Black voters in Michigan, Ohio and Pennsylvania helped propel President Barack Obama to victory in 2012, when black voter turnout rates surpassed white voter rates for the first time. While Clinton has enjoyed the overwhelming support of black voters in southern states, those traditionally red states are unlikely to help the Democratic nominee during the general election, making black voter support and turnout in northern states key for the Democratic Party in November.

Clinton picked up wins in Florida, North Carolina, Ohio and Illinois. The race in Missouri remains too close to call but Clinton is projected to win in the state. In those states, cities with large black communities including Chicago with 32.9 percent African-American residents, Cleveland with 53.3 percent, St. Louis with 49.2 percent, Fayetteville, North Carolina, with 41.9 percent and Miami Gardens, Florida, with 76.3 percent, could serve as bellwethers for how Clinton is being viewed by voters heading into the general election and whether Democrats will be able to count on black voters to turn out in large numbers in swing states in November.

Eight out of 10 black voters supported Clinton in North Carolina, while in Florida she picked up over almost 80 percent of the black vote, according to national exit polls cited by FiveThirtyEight. In Illinois, Clinton picked up support from 70 percent of black voters, while support dropped to 68 percent from black voters in Ohio. In Missouri, where black Democrats make up one-fifth of the party's voters, she picked up approximately 65 percent support from black voters to Sanders' 33 percent, a near repeat of results in Michigan last week.

Clinton has won the black vote by wide margins in many southern states, such as in South Carolina, where she got 73.5 percent to Bernie Sanders' 6 percent, but support narrows in northern states where black voters make up a smaller percentage of the Democratic base. Black voters make up 12 percent of the U.S. population, but they made up 13 percent of the electorate in 2012.

After Sanders’ surprise win last week in Michigan, Clinton’s campaign will be closely watching to see how she can gain a larger percentage of support in northern states. While Clinton captured the black vote in Michigan, 65 percent to 31 percent, it was a smaller margin than seen in earlier primaries held in southern states, the Detroit Free Press reported. Black voters made up less than a quarter of voters in Michigan.

Older black voters have overwhelmingly supported Clinton, while younger voters are more likely to be torn between the two Democratic candidates. Clinton has focused campaign efforts on reaching out to black communities, building on her husband Bill Clinton's success with black voters during his two terms in office from 1993 to 2001. Sanders has highlighted his own work during the civil rights movement in an effort to appeal to voters.