Story highlights Sanders blasts 'unprecedented level of obstructionism against President Obama'

Clinton sidesteps question on releasing transcripts of Wall Street speeches

(CNN) Hillary Clinton and Bernie Sanders confronted issues of race Tuesday at a CNN town hall four days ahead of the South Carolina Democratic primary in which African-American voters will play a crucial role.

Sanders accused Republican presidential front-runner Donald Trump and others of fomenting a "racist effort" to delegitimize President Barack Obama. Sanders portrayed the "birther" controversy that Trump pushed during Obama's first term as part of a Republican strategy to thwart his presidency, based on the mantra "obstruct, obstruct, obstruct."

"We have been dealing in the last seven years with an unprecedented level of obstructionism against President Obama," Sanders said.

Sanders has been criticized by Clinton in recent debates and town halls for not being sufficiently supportive of the President, who remains popular among many Democrats, especially African-Americans. Sanders is under pressure to improve his standing among minorities before South Carolina's primary and the string of Southern contests that follow on March 1, which could tilt the momentum of the Democratic White House race toward Clinton.

The forum highlighted the very different tone Clinton and Sanders take to address race. Sanders called for reforms in the criminal justice system and promised to hike funding for historically black colleges and universities if he is elected president.

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