Former president Bill Clinton is scheduled to headline a rally in Columbia, S.C., on Wednesday night aimed at firing up African American voters, a key constituency in the state's upcoming Democratic primary. The campaign also announced that over the next month, more than 170 black women, from grass-roots activists to elected officials to entertainers, will be dispatched to the Palmetto State and other Southern states.

Clinton, who barely beat Sen. Bernie Sanders (I-Vt.) on Monday in Iowa and is trailing badly in Tuesday's New Hampshire primary, holds a solid lead in South Carolina, which holds its primary Feb. 27, and is polling strong with black and Hispanic voters, who make up a sizable share of Democratic voters in Southern and Western states. More than a dozen Southern and Western states hold nominating contests between Feb. 20 and March 15,  and Clinton is looking to score decisive victories toward winning the party's nomination.

Black voters make up more than half of the electorate in South Carolina, and most of those voters are women. An NBC News/Wall Street Journal/Marist poll released last week showed Clinton leading Sanders among black voters 74 to 17.

A Washington Post/ABC News poll released last week showed Clinton leading Sanders 55 to 36, although that gap was 12 points wider in December.

Sanders has made several visits to South Carolina since the summer, and over the past several days has picked up the endorsements of two African American state lawmakers. Cornel West, a noted black scholar, also has made frequent visits to South Carolina on Sanders's behalf, including holding events at historically black colleges and universities.

The former president campaigned for his wife in South Carolina to disastrous effect in 2008, when Hillary Clinton was engaged in a tough primary battle with then-Sen. Barack Obama. Bill Clinton angered many black political leaders with comments that they said were racially insensitive. Bill Clinton said his comments were misconstrued, but the end result was a break-up between the Clinton and black voters, who had continued to support the president while he was in office in the face of criticism and ethical crises. Obama won South Carolina by a wide margin.

Hillary Clinton, who ended up serving as secretary of state during Obama's first term, has worked hard to repair relationships in South Carolina, and many of the Obama campaign aides who worked against her are now organizing voters on her behalf. The rally featuring Bill Clinton is being held at Allen University, a historically black institution. The president of the school, Lady June Cole, is among the black women leaders who have endorsed Hillary Clinton.

Black women voted at a higher rate than any other demographic group in 2008 and 2012, and the campaign has focused on appealing to them. The roster of endorsers and surrogates includes members of Congress, mayors and other local officials, academics, clergy and business leaders, as well as actresses Angela Bassett, Vivica Fox and Uzo Aduba, and television producer Shonda Rhimes.

The campaign said the women will host events, work phone banks and go door-to-door to "talk about how Clinton will fight for women by working to close the pay gap, fight for paid family leave, make affordable child care a reality, protect women’s reproductive rights, raise the minimum wage and promote women’s rights around the world."