Sen. Bernie Sanders (I., Vt.) stood his ground Sunday morning over a controversial endorsement, saying that the Democratic Party should focus on economic over social issues.

"Face the Nation" host John Dickerson noted there is a debate over prioritization of social and economic issues in the Democratic Party. Sanders and deputy chair of the Democratic National Committee Rep. Keith Ellison (D., Minn.) have come under fire for endorsing Heath Mello, a pro-life Democrat running for mayor in Omaha, Nebraska.

"One of the reasons there's a bit of a debate about the Omaha candidate for mayor is that he is against abortion rights, and so there is a debate about cultural issues versus economic," Dickerson said. "How does the party sort all that out?"

Sanders was quick to defend his party's pro-abortion credentials.

"I have a 100 percent lifetime pro-choice voting record, overwhelming majority of Democrats are pro-choice," Sanders said. "I'm going to do everything that I can to see that the Republicans do not get away with their horrific efforts to defund Planned Parenthood, which provides health care to 2.5 million women."

"But, if we're going to become a 50-state party, if you're going to go to Omaha, Nebraska, which has a Republican governor, two Republican senators, all Republican Congress people, Republican legislature, you know what, and if in Omaha 5,000 or 6,000 people come out to a rally led by Jane Kleeb, their new Democratic chairperson, who is doing a great job, and if you have a rally in which you have the labor movement and environmentalists and Native Americans and the African-American community and the Latino community coming together saying, we want this guy to become our next mayor, should I reject going there to Omaha? I don't think so," Sanders said.

"It was a great rally, and I hope very much he wins," he concluded.

Sanders' endorsement of Mello has produced uproar from pro-abortion groups, as Mello supported anti-abortion legislation during his time in the State Legislature. Mello told the Huffington Post he would not do anything in office to "restrict access to reproductive health care."

Sanders was not the only prominent liberal to be asked about the controversy. House Minority Leader Nancy Pelosi (D., Calif.) told Chuck Todd on NBC's "Meet the Press" that "of course" pro-life Democrats are welcome in the party. The same morning, however, Senate Minority Whip Dick Durbin (D., Ill.) insisted that only people who support Roe v. Wade can be part of the party he leads.