President Trump on Sunday doubled down on his refusal to concede the election to President-elect Joe Biden, even after suffering resounding court defeats over his election challenges and amid a growing popular-vote margin for the Democrat.

“He only won in the eyes of the FAKE NEWS MEDIA,” Trump said of Biden in a morning tweet, providing no evidence to back up his claim. “I concede NOTHING! We have a long way to go. This was a RIGGED ELECTION!”

The president’s declaration comes as he and his administration continue to falsely accuse Democrats of election fraud and impede the transition. It also follows an earlier Sunday morning tweet in which he appeared – if inadvertently – to acknowledge Biden’s win.

President Trump in the Oval Office after speaking about “Operation Warp Speed” in the Rose Garden at the White House on Friday. Jabin Botsford/The Washington Post

“He won because the Election was Rigged,” Trump said in the tweet. “NO VOTE WATCHERS OR OBSERVERS allowed, vote tabulated by a Radical Left privately owned company, Dominion, with a bad reputation & bum equipment that couldn’t even qualify for Texas (which I won by a lot!), the Fake & Silent Media, & more!”

As with his other accusations, Trump did not provide any evidence, and Twitter quickly flagged the tweet, noting that his “claim of election fraud is disputed.”

Asked whether Trump’s original tweet was a sign that he is acknowledging defeat, Rudy Giuliani, the president’s personal attorney, said, “No, no, no. Far from it.” The president was being “sarcastic,” Giuliani said on Fox News Channel’s “Sunday Morning Futures.”

In remarks in Wilmington, Del., last week, Biden weighed in on Trump’s refusal to concede the race, denouncing the president’s actions and suggesting that Americans are “ready to unite.”

“Well, I just think it’s an embarrassment, quite frankly,” Biden said of Trump’s insistence that he won the race. Biden added that Trump’s actions “will not help the president’s legacy.”

On Sunday, Biden’s incoming chief of staff, Ron Klain, said the president-elect did not win because of fraud – “he won because he got more votes.”

“He won the same number of electoral votes that President Trump himself called a landslide four years ago,” Klain said. “But look, if the president’s prepared to begin to recognize that reality, that’s positive. Donald Trump’s Twitter feed doesn’t make Joe Biden president or not president. The American people did that.”

Sen. Bernie Sanders, I-Vt., who lost to Biden in the Democratic primary and has since become a forceful supporter of his candidacy, said Sunday that the president’s refusal to concede and his perpetuation of false claims of fraud are “absolutely disgraceful” and “un-American.”

“I would just hope to God that he has the decency in him to man up and say, ‘You know what, we fought hard. We lost the election. Good luck to Joe Biden. I love America,’ ” Sanders said. “But the fact that he is not even cooperating in the transition – the fact that he continues to deny reality and continues to suggest that Biden has illegally won the election – is beyond belief, in terms of the behavior for an American president.”

Trump and his allies filed lawsuits in five key states. But rather than revealing fraud, the effort by Trump’s legal team has so far done the opposite: It has affirmed the integrity of the election. Nearly every GOP challenge has been tossed out, and not a single vote has been overturned.

While most Republican lawmakers and officials have refused to acknowledge that Biden won the race, some on Sunday said their party needs to accept reality.

In an appearance on NBC News’s “Meet the Press,” Arkansas Gov. Asa Hutchinson said that he expects Biden will be the next president of the United States and that Trump should allow the transition to proceed smoothly.

“It’s important that we accept the outcome of the election,” Hutchinson said. He noted that Trump probably does not want to concede while some of his legal challenges remain unresolved, but he added, “We need to come together as a nation.”

John Bolton, Trump’s former national security adviser, called on Republican leaders to explain to their voters that the president’s claims about the election are unsubstantiated.

“The fact is we’ve seen litigation in all the key battleground states, and it has failed consistently,” Bolton said in an interview on ABC News’s “This Week.” He added: “If the Republican voters are only hearing Donald Trump’s misrepresentations, it’s not surprising they believe it. It’s critical for other Republican leaders to stand up and explain what actually happened. Donald Trump lost what, by any evidence we have so far, was a free and fair election.”

Bolton noted that the Trump campaign’s “basic argument is this was a conspiracy so vast and so successful that there’s no evidence of it.”

“If that’s true, I really want to know who these people are that pulled this off,” he said. “We need to hire them at the CIA.”