Jimmy Carter congratulates Joe Biden and Kamala Harris on election win

Former U.S. President Jimmy Carter speaks to the congregation at Maranatha Baptist Church before teaching Sunday school in his hometown of Plains, Georgia.

Former President Jimmy Carter and first lady Rosalynn Carter have congratulated Joe Biden on his victory in the 2020 election.

In a statement through the Carter Center, the former president from Georgia congratulated Joe Biden and Kamala Harris, who Carter called "friends."

"Rosalynn joins me in congratulating our friends President-elect Joe Biden and Vice President-elect Kamala Harris," Jimmy Carter said. "We are proud of their well-run campaign and look forward to seeing the positive change they bring to our nation."

Biden's victory came after more than three days of uncertainty as election officials sorted through a surge of mail-in votes that delayed the processing of some ballots. Biden crossed 270 Electoral College votes with a win in Pennsylvania.

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Trump refused to concede, threatening further legal action on ballot counting.

Biden, 77, staked his candidacy less on any distinctive political ideology than on galvanizing a broad coalition of voters around the notion that Trump posed an existential threat to American democracy. The strategy proved effective, resulting in pivotal victories in Michigan and Wisconsin as well as Pennsylvania, onetime Democratic bastions that had flipped to Trump in 2016.

Joe Biden and Kamala Harris: Reaction pours in after historic projected White House win

Biden, in a statement, said he was humbled by the victory and it was time for the battered nation to set aside its differences.

“It’s time for America to unite. And to heal,” he said.

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“With the campaign over, it’s time to put the anger and the harsh rhetoric behind us and come together as a nation,” Biden said. “There’s nothing we can’t do if we do it together.”

Biden was on track to win the national popular vote by more than 4 million, a margin that could grow as ballots continue to be counted.

Trump was not giving up.

Departing from longstanding democratic tradition and signaling a potentially turbulent transfer of power, he issued a combative statement while he was on his Virginia golf course. It said his campaign would take unspecified legal actions and he would “not rest until the American People have the honest vote count they deserve and that Democracy demands.”

Trump has pointed to delays in processing the vote in some states to allege with no evidence that there was voter fraud and to argue that his rival was trying to seize power — an extraordinary charge by a sitting president trying to sow doubt about a bedrock democratic process.

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Kamala Harris also made history as the first Black woman to become vice president, an achievement that comes as the U.S. faces a reckoning on racial justice. The California senator, who is also the first person of South Asian descent elected to the vice presidency, will become the highest-ranking woman ever to serve in government, four years after Trump defeated Hillary Clinton.

Trump is the first incumbent president to lose reelection since Republican George H.W. Bush in 1992.

The Associated Press contributed to this report.