Clinton retweets Sanders’s attack on Trump
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Democratic front-runner Hillary ClintonHillary Diane Rodham ClintonJustice to provide access to Comey memos to GOP lawmakers Justice Dept inspector asks US attorney to consider criminal charges for McCabe: reports 'Homeland' to drop Trump allegories in next season MORE showed a rare moment of unity with rival Sen. Bernie SandersBernard (Bernie) SandersSanders, Warren, O’Rourke inspire patriotic small donor waves Bill Press reflects on Clinton, Sanders and a life in politics Overnight Health Care: GOP pushes stiff work requirements for food stamps | Johnny Isakson opens up about family's tragic loss to opioids | Republicans refuse to back vulnerable Dem's opioids bill | Dems offer new public option plan MORE (I-Vt.), as the two landed on the same side regarding Donald TrumpDonald John TrumpHouse Republicans push Mulvaney, Trump to rescind Gateway funds Pruitt spent K flying aides to Australia to prep for later-canceled visit: report Rosenstein told Trump he is not a target of Mueller probe: report MORE’s delay in denouncing the Ku Klux Klan this week.

“America's first black president cannot and will not be succeeded by a hatemonger who refuses to condemn the KKK,” Sanders tweeted, which Clinton's account retweeted several minutes later.

Trump, who is increasingly seen as the GOP’s likely nominee, has walked into a firestorm of criticism this week after receiving an endorsement from white supremacist David Duke.

As recently as Sunday morning, Trump had declined to condemn Duke’s racism. In an interview with CNN’s “State of the Union” on Sunday morning, Trump avoided a question about whether he'd condemn Duke's racism.

Later Sunday afternoon, Trump took to Twitter to formally denounce the former Ku Klux Klan grand wizard’s endorsement.