(CNN) — Outgoing Indiana Democratic Sen. Joe Donnelly said Democrats need to be careful in promoting too many progressive ideas in red states like his because they’ll “start losing the people in my state.”

“Medicare-for-all” is a progressive stance that some Democrats worry could alienate Midwestern voters from the party going into the 2020 presidential election. It has become popular thanks to liberal leaders like Vermont Sen. Bernie Sanders.

When asked by CNN’s Dana Bash on “The Lead With Jake Tapper” if Democrats could be viable without appealing to interior state votes, Donnelly replied, “I don’t know how you do that.”

Donnelly said that during President Donald Trump’s visits to Indiana in the weeks before the midterms — in which Donnelly lost his seat — the President made not voting for Republicans seem like a personal betrayal by voters.

“We have not made enough of a connection … that the people of my state understand culturally, we (Democrats) want to make sure you succeed,” he said.

“But when you talk ‘Medicare-for-all’ …you start losing the people in my state,” Donnelly added. “When we start talking about, ‘Hey, we’re going to work together with the insurance companies to lower premiums,’ that’s what connects.”

“The talk on the coasts just doesn’t get it done in the middle,” he said.

“Medicare-for-all” has become a contentious issue for Democrats as they prepare to assume the majority in January. Some new House Democrats, such as Democratic socialist Rep.-elect Alexandria Ocasio-Cortez, championed the issue on the campaign trail despite trepidation from other parts of the party. But Minority Leader Nancy Pelosi has indicated that she is open to considering a more public option during the new Congress.

Republicans have seized on the buzzword, arguing that “Medicare-for-all” would threaten the program’s availability for seniors. Trump published an op-ed just before the midterms bashing Democrats for threatening to “eviscerate” the program with such an expansion.

Looking ahead to the presidential election, Donnelly cautioned that “who wins the primary is not necessarily the best person in a general election.”

While he declined to name a specific candidate he thought would fare best, Donnelly said the ideal candidate would engage directly with people in the interior states on issues such as manufacturing and health care.

They would be the “kind of person who can go into Michigan and go to the auto plant” and have “talked to the workers there, and have talked to the families at the churches and have talked to them about how important it is for their kid to get decent health care,” he said.

“People want to make sure they have a good job, decent health care, that they can retire with dignity and that they know that the future is better for their children and grandchildren,” Donnelly added. “When we talk about those things, we have success in the Midwest.”

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