The only senator to endorse Sen. Bernie Sanders (I-VT) is “absolutely” opposed to a convention-floor battle to flip superdelegates who support Hillary Clinton.

Sen. Jeff Merkley (D-OR) told the Washington Post on Wednesday that Sanders should bow out if Clinton wins a higher number of pledged delegates as well as the popular vote.

“When a nominee wins a majority of both those categories, it is time for us to come together, link arms and go forward,” Merkley said. “It would be inconsistent, given the commentary on super-delegates, to depend on super-delegates to turn over those first two categories of evaluating party members’ support.”

While the Sanders campaign and its supporters initially criticized superdelegates—party insiders who can change their allegiance to a particular candidate—as undemocratic, top aides are now betting the future of the campaign on convincing those delegates to join their side.

Sanders campaign manager Jeff Weaver said on MSNBC last week that it was “a fact” that superdelegates would decide the nomination.

“Nobody is going to get to the convention with the number of pledged delegates they need to win,” Weaver said. “That’s just mathematically impossible for either candidate.”

As of Thursday, Clinton was 90 delegates short of the 2,383 needed to win the nomination outright, while Sanders was 850 delegates short. Clinton has secured 1,768 pledged delegates out of 2,293 total, compared to Sanders’ 1,494 out of 1,533.

Clinton also leads the popular vote with 12,989,134 votes to Sanders’ 9,957,889.

Top Sanders adviser Tad Devine was noncommittal when asked by the Washington Post’s Greg Sargent whether the campaign would help convince Sanders supporters that the election’s outcome was legitimate.

“We’re still involved in this process, so it’s hard for me to declare what’s going to happen at the end,” Devine said. “As we look forward, there are a lot of issues of deep concern.”