Sen. Bernie Sanders, I-Vt., is not apologizing for campaigning for an anti-abortion candidate, despite outrage from pro-abortion rights Democrats.

Pro-abortion groups blasted the 2016 Democratic presidential candidate for campaigning for Omaha, Neb., mayoral candidate Heath Mello, who has backed measures as a state senator to restrict abortion access.

Sanders argued that to protect abortion rights, Democrats need to win at the state and local level, and sometimes that requires supporting a more popular conservative candidate. Mello supported a 2009 bill requiring doctors to inform women seeking abortions about the availability of ultrasound.

"If we are going to protect a woman's right to choose, at the end of the day we're going to need Democratic control over the House and the Senate, and state governments all over this nation," Sanders told NPR. "And we have got to appreciate where people come from, and do our best to fight for the pro-choice agenda. But I think you just can't exclude people who disagree with us on one issue."

"The actions today by the DNC to embrace and support a candidate for office who will strip women – one of the most critical constituencies for the party – of our basic rights and freedom is not only disappointing, it is politically stupid," NARAL Pro-Choice America President Ilyse Hogue said. "Today's action makes this so-called 'fight back tour' look more like a throw-back tour for women and our rights."

For its part, the Democratic National Committee is appearing to distance itself from Sanders' endorsement of Mello, quickly telling reporters it was the senator's idea to hold the rally and not the DNC's.

DNC Chairman Tom Perez has joined Sanders in touring states President Trump won, in what has been dubbed as a unity tour. Perez did not join Sanders for the endorsement of Mello and was attending a fundraiser in Georgia for Democrat Jon Ossoff, who is facing a June 20 runoff election to fill the House seat left by Health and Human Services Secretary Tom Price.