Clinton, 68, a former secretary of state, and Sanders, 74, an independent US senator from Vermont who ran for president as a Democrat, waged a bruising months-long battle for the nomination. Branding himself a democratic socialist, Sanders galvanized young and liberal voters with his calls to rein in Wall Street and eradicate income inequality.
But Sanders repeatedly voiced frustration with a DNC and party establishment he felt was stacked against him, and the resentment from Sanders and his supporters threatened to disrupt the convention.
"I'm not shocked but I'm disappointed," Sanders said of the emails earlier on Sunday on ABC's "This Week."
The emails showed DNC officials pondering various ways to undercut Sanders. Brad Marshall, the DNC's chief financial officer, apologized on Facebook on Saturday for an email in which he discussed how some voters in upcoming nominating contests in Kentucky and West Virginia would reject an atheist.
"He had skated on saying he has a Jewish heritage," Marshall wrote in a May 5 email to three top DNC officials. No names were mentioned, but Sanders was the only Jewish candidate.
"I think I read he is an atheist. This could make several points difference with my peeps. My Southern Baptist peeps would draw a big difference between a Jew and an atheist."
Clinton told CBS's "60 Minutes" in an interview that aired on Sunday that she had not read any of the emails but it was "wrong and unacceptable" to bring religion into the political process.