Democratic presidential candidates Sen. Bernie Sanders and Hillary Clinton participate in a PBS debate at the University of Wisconsin-Milwaukee on Thursday. (Win McNamee/Getty Images)

Hillary Clinton’s role in a two-decade-old crime bill has emerged as a major point of criticism among supporters of Sen. Bernie Sanders, who say the legislation accelerated the racial disparities that are at the heart of the movement by young black activists demanding criminal justice reform.

But Sanders was not an innocent bystander, Clinton supporters argue, noting he voted for the bill that is now widely criticized for having pushed the nation's prison population to more than 6.8 million in 2014, up from 5.5 million in 1996, according to federal statistics.

Democratic presidential candidates Bernie Sanders and Hillary Clinton called for criminal-justice reform for African Americans in policing, jobs and housing during the PBS NewsHour debate on Feb. 11. The debate comes as both candidates try to pitch themselves to black voters. (PBS NewsHour)

President Bill Clinton championed and signed the 1994 Violent Crime Control and Law Enforcement Act, which created longer mandatory sentences, reclassified less serious crimes as felonies and put tens of thousands more police officers on the streets.

As first lady, Hillary Clinton advocated for the bill, and critics say she bears responsibility for the way it has resulted in a disproportionate number of African Americans and Hispanics being ensnared in the criminal justice system. Mandatory minimum sentences, particularly for nonviolent drug crimes, were disproportionately meted out to black and Hispanic offenders. African Americans and Hispanics also are more likely than white people to be stopped by police.

But Sanders, at the time a member of the House, supported the bill, a fact that Clinton supporters have noted as they seek to blunt the Vermont senator’s newly aggressive push for black voters. Having crushed Clinton in New Hampshire and nearly tied with her in Iowa, the Sanders campaign is hoping to grab the attention of African American and Hispanic voters, who make up significant shares of Democratic voters in upcoming primary and caucus states.

On Feb. 20, Democrats will caucus in Nevada, where Hispanic voters are estimated to be 20 percent of the electorate. In South Carolina, which holds its primary Feb. 27, African Americans make up more than half the Democratic electorate.

Clinton has held a wide lead over Sanders among black voters, and in recent days Sanders has announced endorsements by high-profile African Americans, including Benjamin Jealous, the former head of the NAACP.

Jealous has noted the Clintons’ actions in ushering in the era of mass incarceration and praised Sanders for having put forth a racial justice platform. Michelle Alexander, whose book “The New Jim Crow” helped launch the current debate over mass incarceration’s impact on the black community, penned an article for The Nation this week arguing that Clinton doesn’t deserve the support of black voters. Both also criticized her for a 1996 speech in which she talked about some teenage offenders as “super predators,” who were beyond rehabilitation and “must be brought to heel.”

Eric Holder, the nation’s first African American attorney general and a Clinton supporter, suggested that a wave of street crime in the late 1980s through the mid-'90s, much of it related to drug trafficking, had alarmed citizens and lawmakers alike.

“Many supported the crime bill because of the circumstances at the time. Sen. Sanders voted for the bill. He has not acknowledged or apologized for his vote. Hillary Clinton, on the other hand, has acknowledged the racially disproportionate impacts of overly harsh crime policy for many years, and worked in the Senate to reform the criminal justice system,” Holder said in a statement to The Washington Post. "As Attorney General, I worked with President Obama to address mass incarceration, and I know Hillary Clinton is the one to continue that work and get it done. She knows our criminal justice system is broken and will make real reforms."

The Sanders campaign, in statement to The Post said, “No candidate running for president has as deep and consistent a record of fighting for civil rights and criminal justice reform as Bernie Sanders. He strongly opposed elements of the 1994 Crime Bill that would lead to mass incarceration and onerous mandatory sentencing requirements.”

“However, there were too many important provisions within the bill for Sen. Sanders to cast a vote against the entire package. Importantly, the bill contained an assault weapons ban that Sen. Sanders supported — which even turned him into a target for the NRA during his reelection — as well as the crucial Violence Against Women Act.”

Clinton made criminal justice reform the first major policy speech after formally announcing her campaign last year. In the speech, which occurred in the midst of unrest in Baltimore after Freddy Gray, an unarmed black man, died after sustaining a spinal cord injury while in police custody. Clinton said, “We have to come to some hard truths about race and justice in America.”

Sanders’s embrace of criminal justice reform in his campaign was more dramatic. Last summer, Black Lives Matter activists twice publicly confronted Sanders for focusing on economic inequality over institutional racism.

Symone Sanders, who had been recently hired as his national spokeswoman, counseled the senator on the importance of acknowledging the role of race in the challenges facing African Americans. Bernie Sanders embraced the issues and language of the young activists, reciting the names of African Americans who had died at the hands of law enforcement and decrying the racial disparities in police stops, sentencing for drug offenses and incarceration rates.

But several prominent African American lawmakers who have endorsed Clinton suggest that Sanders is a recent convert to the cause.

South Carolina House Democratic Leader J. Todd Rutherford said Sanders “has not always had our back” on criminal justice issues. “He voted for the 1994 crime bill. We have yet to receive an apology from Sen. Sanders," Rutherford said. "Sen. Clinton has spent her entire life fighting for criminal justice issues.”

Khalil Muhammad, a leading scholar on the political, social and economic links between race and crime, said the 1994 crime bill was “a signature accomplishment for Bill Clinton and not the same as a congressman voting for a bill.”

He credited the “activism of people on the ground, in their communities, fighting against the ravages of mass incarceration and all its collateral damage” in pushing the issue to the forefront of the 2016 presidential  election. “This debate about the criminal justice system both in terms of what we’re going to do about it and how we got here is incredibly healthy.”

So far, neither Clinton nor Sanders has directly criticized the other for their roles in the crime bill. (Vice President Biden, who was courted heavily by some in his party to run for president this year, sponsored the bill as head of the Senate Judiciary Committee.)

Instead, the candidates have talked about their respective criminal justice reform plans, and in recent weeks have touted the support of relatives of the unarmed African Americans who have been killed in encounters with white police officers and civilians.

This week, the Sanders campaign unveiled a four-minute video of Erica Garner, whose father, Eric Garner, died after being placed in a chokehold by a New York City police officer.

Gwen Carr, the slain man's mother, is supporting Clinton, who also this week went on the air in South Carolina with a campaign ad criticizing the criminal justice system as "fundamentally broken."