African-Americans are not turning out to vote early in large numbers as they did for President Obama's candidacy four years ago, raising concerns for Hillary Clinton in crucial battleground states with just six days left until Election Day.

The first full weekend of in-person early voting came to a close on Sunday, revealing a slump among African-American voters who overwhelmingly support Clinton over Republican presidential candidate Donald Trump.

Low voter turnout among African-Americans is particularly bruising to Clinton in key swing states like Florida, North Carolina, and Ohio.

Early polls over the weekend showed that voter turnout among blacks in North Carolina fell by 16 percent since 2012 while white turnout rose by 15 percent, the New York Times reported Tuesday.

Black participation has fallen in Florida from 25 percent four years ago, to 15 percent in the current election. In Ohio, voter turnout among African-Americans has also fallen in largely Democratic areas near Cleveland and Columbus. The slumped turnout could irreversibly harm Clinton's campaign, which is dependent on African-American support in order to outpace Trump on Nov. 8.

Democratic Rep. Alcee Hastings, who represents one of the largest black communities in south Florida, told Politico the Clinton campaign has failed to deploy sufficient outreach in predominantly African-American areas.

"I have been screaming for months about this and nothing changed and now look what's happening," Hastings said.

Obama is visiting North Carolina on Wednesday before heading to Miami and Jacksonville, Fla. on Thursday in a last minute push to urge African-Americans to vote for Clinton.