Story highlights Jeff Merkley said Bernie Sanders should drop out if his nomination path is closed after California

Merkley is Sanders' only supporter in the 46-member caucus

(CNN) Bernie Sanders' lone supporter in the Senate said Thursday that the Vermont senator should end his presidential campaign if he's losing to Hillary Clinton after the primary season concludes in June, breaking sharply with the candidate who is vowing to take his insurgent bid to the party convention in Philadelphia.

In an interview with CNN, Oregon Sen. Jeff Merkley argued that the party should be united heading into the July convention. And that if Sanders has no viable path to the nomination after the final round of primaries in June, he should concede to Clinton at that point. He said that Sanders should follow the model employed by Clinton in 2008, who dropped out in June of that year and pledged her support to Barack Obama.

"Secretary Clinton, then senator, said, 'OK, I had the discussion across America. I'm ready to pivot and work together.' And Obama reached out, and she reached out, and that should be a model for us to follow," Merkley said outside of the Capitol on Thursday. "I think after California, June 7, is about the time it would be appropriate -- all states will have weighed in by then. It will then give them five weeks to work together" before the convention.

Asked if that meant he believed Sanders should drop out if he has no viable path to the nomination after the June primaries, Merkley said, "Yes."

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