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President-elect Joe Biden on Saturday night claimed "a clear victory" and preached unity in Wilmington, Del., after earlier in the day taking a projected victory in a contentious presidential election. 

The remarks by Biden came hours after the Fox News Decision Desk projected that he and Vice President-elect Kamala Harris would defeat President Trump and Vice President Mike Pence, denying them a second term. 

"The people of this nation have spoken. They delivered us a clear victory. A convincing victory. A victory for we the people," Biden said. "The most votes ever cast for a presidential ticket in the history of this nation."

President-elect Joe Biden addresses supporters for first time after projections that he will win election

Biden was projected as the winner of the presidential election after days of vote-counting, securing more than 75 million votes, just over 50% of the national popular vote. As of Saturday evening, he is projected to get at least 290 electoral votes with a handful more on the table. 

Biden's claim of victory, however, is not uncontested. In one tweet Saturday, despite the vote totals favoring Biden, Trump said "I WON THIS ELECTION, BY A LOT!"

Biden called the celebrations that broke out across the country Saturday "an outpouring of joy, hope, renewed faith that tomorrow will bring a better day."

"I pledge to be a president who seeks not to divide but unify. Who doesn't see red states and blue states, only sees the United States."

To make progress we have to stop treating our opponents as our enemies. They are not our enemies, they are Americans

— President-elect Joe Biden

To Trump supporters, he said: "I understand the disappointment tonight. But now let's give each other a chance. It's time to put away the harsh rhetoric, lower the temperature... To make progress we have to stop treating our opponents as our enemies. They are not our enemies, they are Americans."

The president-elect also said he wants the parties to begin "to cooperate with one another," calling polarization between the parties "a choice."

"If we can decide not to cooperate, then we can decide to cooperate," Biden said, claiming cooperation as part of the "mandate" from his election. "They want us to cooperate in their interest, and that's the choice I'll make."

Also part of Biden's mandate, he said, is to address the coronavirus crisis, an issue that defined the presidential campaign and which many say potentially led to his victory.

"Our work begins with getting COVID under control," Biden said, noting his plan to announce a panel of coronavirus advisers for his transition team. He added that Americans will not be able to experience "all the moments that matter most to us until we get it under control."

Vice President-elect Kamala Harris arrives to speaks Nov. 7, in Wilmington, Del. (AP Photo/Carolyn Kaster)

Projections showed Biden winning in Pennsylvania and Nevada, which put him over the 270 electoral votes required to win the presidency. 

Biden is the oldest person ever elected to the presidency. Harris is the first woman elected to the vice-presidency. 

Ahead of Biden's speech, music was playing and supporters were dancing at the event. The campaign passed out glow sticks and American flags to supporters. There are some 400 cars at the event, most of which are adorned with Biden-Harris signs. Supporters loudly honked their horns as Harris took the stage. 

"When our very democracy was on the ballot this election, with the very soul of America at stake," Harris told supporters. "You ushered in a new day for America."

"For four years you marched and organized for equality and justice. And then you voted. And you delivered a clear message. You chose hope and unity, decency, science and yes, truth."

While I may be the first woman in this office, I will not be the last

— Vice President-elect Harris

Harris also addressed the history of the moment, as she is set to break one of the highest glass ceilings in American society. 

"While I may be the first woman in this office, I will not be the last," she said. "Because every little girl watching tonight sees that this is a country of possibilities."

Regarding Harris, Biden lauded that she is the "first daughter of immigrants ever elected in this country. Don't tell me it's not possible in the United States." 

Biden's unifying tone follows a contentious campaign, one during which Trump consistently hammered him with personal attacks.

Vice President-elect Kamala Harris addresses supporters Saturday night after Fox News Decision Desk called the presidential election for Joe Biden earlier in the day

BIDEN WINS PRESIDENCY, TRUMP DENIED SECOND TERM IN WHITE HOUSE, FOX NEWS PROJECTS 

"America, I’m honored that you have chosen me to lead our great country," Biden said in a Saturday tweet. "The work ahead of us will be hard, but I promise you this: I will be a president for all Americans — whether you voted for me or not. I will keep the faith that you have placed in me."

Biden will enter office on Jan. 20 at the head of a divided nation, after a year that included an impeachment trial for Trump, a pandemic that has killed over 200,000 people, race-related protests and riots and more. He will also helm a Democratic Party in which many are calling for radical change and an  progressive agenda. 

But Biden has been resistant to that, remaining steadfast in his opposition to things like banning fracking or eliminating private health insurance. 

The Biden event Saturday night was drive-in style, like many of his campaign events have been. It comes after a day of general silence from the president, outside of a handful of tweets. 

Trump has not yet conceded the race and is planning to pursue recounts and legal challenges in multiple states.

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"We all know why Joe Biden is rushing to falsely pose as the winner, and why his media allies are trying so hard to help him: they don’t want the truth to be exposed," a statement from Trump Saturday read. "Beginning Monday, our campaign will start prosecuting our case in court to ensure election laws are fully upheld and the rightful winner is seated. The American People are entitled to an honest election: that means counting all legal ballots, and not counting any illegal ballots."

But those challenges are extremely unlikely to lead to a positive electoral result for the president. 

Even if some misconduct or fraud is found, and some votes are changed or thrown out, it appears impossible that any such challenges could close the gaps between Biden and Trump in those states, based on the history of past recounts and legal challenges. Those efforts would also need to succeed in multiple states, in contrast to Al Gore's 2000 challenge which was only in Florida. 

Fox News' Allie Raffa contributed to this report.