In the ostensibly friendly battle between the more than twenty candidates now running for the Democrat's presidential nomination, the battle over who is "most progressive" has emerged as one theme that makes the 2020 primary race stand apart from previous election years.

And while former vice president Joe Biden, largely considered the frontrunner in the field despite only entering the race officially just last month, made headlines for claiming he should be granted that title, Sen. Bernie Sanders on Sunday morning pushed gently back on that idea.

"Look Joe Biden is a good friend of mine and I'm not here to attack Joe," said Sanders when asked about the issue by ABC News' Jonathan Karl during an interview in Iowa on Sunday morning. In response to the question, Sanders said their distinct voting records when they served together in the Senate speak for themselves.

"Joe voted for the war in Iraq, I led the effort against it. Joe voted for NAFTA and Permanent Normal Trade Relations [PNTR] with China, I led the effort against that. Joe voted for the deregulation of Wall Street, I voted against that," Sanders said. "You know, I think if you look at Joe's record and you look at my record, I don't think there's much question about who's more progressive."

Watch:

Bernie is right. When Joe Biden says he’s the most progressive candidate running for President it can only lead me to believe that Joe doesn’t even know what it means to be progressive. SCROLL TO CONTINUE WITH CONTENT Never Miss a Beat. Get our best delivered to your inbox.





He’s literally the least progressive major candidate. pic.twitter.com/ntGpyQ5AlT — Shaun King (@shaunking) May 5, 2019

Biden's initial comment about being the "most progressive" candidate came in March, before he announced his run: