Donald Trump refuses to condemn KKK - and Marco Rubio's backers pounce

The Republican presidential race landed in dicier territory Sunday as frontrunner Donald Trump went before a national audience on CNN and refused to condemn the Ku Klux Klan or disavow an endorsement from ex-Klansman David Duke.

The billionaire told Jake Tapper on CNN's "State of the Union" that he knows "nothing about David Duke. I know nothing about white supremacists."

Trump was pressed three times on whether he'd distance himself from the Ku Klux Klan -- but never mentioned the group in his answers.

"I don't know anything about what you're even talking about with white supremacy or white supremacists," he said. "So I don't know. I don't know -- did he endorse me, or what's going on? Because I know nothing about David Duke; I know nothing about white supremacists."

The Anti-Defamation League had called on Trump to repudiate the support of Duke, the former grand wizard of the Ku Klux Klan, and other white supremacist groups. Asked if he'd broadly distance himself from those groups, Trump demurred, saying he knew nothing about their support for his bid for the Republican presidential nomination.

Trump was then asked specifically asked if he would disavow the KKK.

"You may have groups in there that are totally fine and it would be very unfair," he said. "So give me a list of the groups and I'll let you know."

A few hours later, Trump tweeted "I disavow" of Duke's support.

Florida Sen. Marco Rubio's campaign, sensing an opening two days before Georgia and other Super Tuesday states vote,  pounced soon after the CNN interview. South Carolina Sen. Tim Scott, a Rubio backer, called this morning to say Trump missed a surefire chance to slam a hate group.

"If there's ever an easy homerun it's disavowing the KKK. That's just called common sense. At the end of the day, it's not a question of history, it's a question of hate. That's an easy call that Donald missed," said Scott, the first black U.S. senator elected from the Deep South since Reconstruction.

"It's very odd," added Scott, who is in Georgia Sunday to rally Rubio supporters. "This has been an interesting campaign season anyways. And at the end of the day, we need to focus on how we create a better America for everyone. And racism is not part of that process."

In Georgia, a state Rep. Tommy Benton came under fire in January for saying the KKK "made a lot of people straighten up." He soon withdrew three controversial pieces of legislation and a conservative radio host offered to back a challenge.