Joe Biden continued to argue on ABC's "This Week" Sunday that the Democratic Party would have a harder time defeating President Trump if it nominates Bernie Sanders, who labels himself a democratic socialist, but stated that he would "work like hell" for the Vermont senator if he wins.

Why it matters: The divide between the moderate and progressive wing of the party has reignited debate over whether voters from each side would ultimately back the nominee against Trump.

The exchange:

BIDEN: "Bernie calls himself a democratic socialist. ... Are you going to win with the label? Are you going to help somebody in Florida win, with the label democratic socialist? Because it's going to go all the way down the line. That's what's going to happen. Are you going to win in North Carolina? Going to win in Pennsylvania? Are you going to win in those states and the Midwest? I didn't put the label on Bernie. Bernie calls himself a democratic socialist.

GEORGE STEPHANOPOULOS: "So you think, flat out, Democrats can't defeat Trump if they have to defend socialism?"

BIDEN: "I think it's going to be incredibly more difficult. Look, if I don't get the nomination and Bernie gets it, I'm going to work like hell for him. But I tell you what, it's a bigger uphill climb running as a senator or a congressperson or as a governor on a ticket that calls itself the democratic socialist ticket."

The big picture: Trump has already made clear that his campaign message for 2020 will center on defeating socialism, regardless of whether the nominee is Sanders or one of the more moderate Democratic candidates.

At his third State of the Union address last week, Trump declared that the United States will "never be a socialist country."

"Socialism destroys nations," he said. "But always remember, freedom unifies the soul."

Go deeper: