Eliza Collins

USA TODAY

Late Tuesday night, Bernie Sanders vowed to continue the fight in the Democratic race all the way to the convention. But after Hillary Clinton became the presumptive Democratic nominee, some of the Vermont senator’s supporters are saying it’s time to give it up.

Oregon Sen. Jeff Merkley (the only senator backing Sanders) told The Washington Post Clinton had locked it up, and it was time to work on unity.

“Once a candidate has won a majority of the pledged delegates and a majority of the popular vote, which Secretary Clinton has now done, we have our nominee,” Merkley said. “This is the moment when we need to start bringing parts of the party together so they can go into the convention with locked arms and go out of the convention unified into the general election.”

Sanders, on Tuesday, told NBC News that his campaign was “on the phone” calling superdelegates to get them to switch their vote. But Merkley said it was time to end that fight: “I would not support a battle that involves trying to flip superdelegates.”

Actor Mark Ruffalo, who has been a prominent supporter of the Vermont senator, tweeted congratulations to Clinton and her supporters on Wednesday and said it was time to focus on pushing for progressive values.

Arizona Rep. Raúl Grijalva, also told The Washington Post that it was time to accept Sanders would not be the nominee.

“The reality is unattainable at some point. You deal with that. Bernie is going to deal with this much more rapidly than you think,” Grijalva said. “At some point, when we’re trying to flip 400 super-delegates, and it’s not gaining traction, I think you have to come to the conclusion that it’s not going to happen. You just move into a different direction. And that different direction is that we begin to try to integrate the party.”

“He’s gonna do the right thing,” Grijalva added.

President Obama — who has stayed out of endorsing during the primary — congratulated Clinton on her victory and Sanders for "energizing millions of Americans" in a White House statement issued late Tuesday.

“The President congratulated Secretary Clinton for securing the delegates necessary to clinch the Democratic Nomination for President. Her historic campaign inspired millions and is an extension of her lifelong fight for middle-class families and children,” the statement from press pecretary Josh Earnest said. “The President thanked Senator Sanders for energizing millions of Americans with his commitment to issues like fighting economic inequality and special interests' influence on our politics.”

Meanwhile, CNN reported that Vice President Biden said it was Sanders’ call on when to leave the race, but that he believed Clinton would be the nominee.

"It's clear we know who the nominee is going to be. I think we should be a little graceful and give him the opportunity to decide on his own,” Biden said.