An aide to Bernie SandersBernie SandersJoe Biden lost his fastball — can he get it back before South Carolina? Where the 2020 Democrats stand on taxes Bloomberg hits Sanders supporters in new ad MORE says the senator will be increasing pressure on superdelegates after Tuesday’s Democratic presidential primary in California.

“We’ve been using a surrogate operation up until now in terms of reaching out to superdelegates,” campaign manager Jeff Weaver said on MSNBC. "Once we get past this part of the process, where people are done voting in California and other states, then we’ll intensify the outreach to the superdelegates.


“I think a lot of superdelegates really, frankly, want to see how the primaries and caucuses turn out. I think you’ll see a lot more intense communication going on in the coming weeks.”

Weaver said Sanders remains the best option for defeating Donald TrumpDonald John TrumpRussian sanctions will boomerang States, cities rethink tax incentives after Amazon HQ2 backlash A Presidents Day perspective on the nature of a free press MORE in a general presidential election this November.

“There’s a case to be made to the superdelegates that he is certainly the strongest candidate in a general election against Donald Trump,” he said of the GOP’s de facto presidential nominee.

“He already has established his validity in going forward. He has over 10 million votes, he has 2.5 million individual contributions, he has run the most successful insurgent campaign in the history of the country outside of President Obama’s.”

Weaver added Sanders would help rally Democrats against Trump should he lose the Democratic presidential nomination to Hillary ClintonHillary Diane Rodham ClintonThe Democratic demolition derby Juan Williams: Don't count Biden out Candidates in Obama's orbit fail to capitalize on personal ties MORE.

“I think he’s absolutely committed to uniting the party going into the fall and beating Donald Trump,” he said of the independent Vermont lawmaker. "There’s no doubt about that.”

Clinton late on Monday crossed the 2,382 delegate threshold for securing the Democratic presidential nomination, according to The Associated Press tally, thanks to the support of superdelegates.

Sanders has repeatedly insisted he will fight on until next month’s Democratic National Convention in Philadelphia.

Sanders’s campaign believes it can win over Democratic superdelegates, who are not bound to any particular White House hopeful.

Clinton leads Sanders in superdelegates nationwide, boasting 571 to his 48 in the latest RealClearPolitics delegates tally.