Six months ago, the independent Vermont senator said, the media considered him a "fringe candidate," making air quotes. | Getty Sanders: Endorsements prove Clinton 'candidate of the establishment'

Hillary Clinton has 31 endorsements in the United States Senate, a body in which her chief rival Bernie Sanders serves. Sanders, meanwhile, who sits at zero such endorsements, said that fact speaks volumes about which of the two Democratic presidential candidates is "prepared to take on the establishment."

"Let's go back six months and look at Bernie Sanders announcing his candidacy and being 3, 4 percent in the polls," Sanders said in an interview with CNN's Gloria Borger aired Monday on "New Day." "No money in the campaign, no volunteers, no political organization, running against a woman who is enormously well-known, whose husband was president of the United States."


"That would be Hillary Clinton," Borger said.

"Oh well, I don't wanna say so, but if you say it," Sanders responded.

Six months ago, the independent Vermont senator said, the media considered him a "fringe candidate," making air quotes.

"Right? Not a serious candidate. Be honest , that was the case," Sanders said. "Now you're saying, you haven't quite won this thing yet. That tells me that we have made real progress in six months."

When Borger brought up the fact that he has not earned any backing from his Senate colleagues, Sanders used it as an opportunity to draw a distinction between himself and the former secretary of state, first lady and New York senator.

"It tells you that one of us is a candidate of the establishment, one of us is involved in establishment politics and establishment economics, and it says that, maybe, the other candidate is prepared to take on the establishment," Sanders remarked.

"That would be you?" Borger asked.

"That would be me, yes. I think that's probably right," the senator said.

Speaking later on the same show, Sen. Claire McCaskill (D-Mo.), who has endorsed Clinton, said Sanders has pushed the former secretary of state to be a "stronger" and "more aggressive" candidate.

Of Sanders, McCaskill said a lot of voters in her state would find it "very hard to look past" Sanders' self-description of being a "democratic socialist."

"Obviously, Bernie is highlighting those issues very well," she said. "I think Hillary Clinton is a better candidate because of it."