The incumbent US President Donald Trump has given every indication that he won't accept the result as fair even as electoral officials have determined Joe Biden as the winner of the 2020 presidential election.
Trump also has refused to commit to a peaceful transfer of power, refusing to concede.
No presidential candidate has ever refused to concede defeat once all the votes were counted and legal challenges resolved. The peaceful transfer of power has been a norm in the US since 1800, when the country's second president John Adams became the first to lose his reelection bid and quietly left Washington, DC, on an early morning stagecoach to avoid attending his successor Thomas Jefferson's inauguration.
Some early presidential candidates did send congratulatory letters to their opponents, says John R Vile, dean of political science at Middle Tennessee State University in Murfreesboro, who has written about the history of concession speeches.
Formal concessions didn't become an election custom until 1896, when Republican William McKinley defeated Democrat William Jennings Bryan. In his account of the campaign in a later memoir, Bryan wrote that he began to resign himself to the loss by 11 pm on election night—a resignation that grew in the subsequent days as states completed counting ballots. On Thursday evening, Bryan learned that his loss was certain and immediately sent a telegram to McKinley, offering his congratulations and stating: "We have submitted the issue to the American people and their will is law."
A custom thus was born - much to Bryan's own bewilderment as he considered it to be simply the courteous thing to do. Ever since losing candidates have conceded to their opponents - even sitting presidents.
Here are concession speeches given by the losing candidates in the past 15 US elections:
1960: Richard Nixon vs John F Kennedy, Kennedy won
Richard Nixon gave a speech as he conceded with the election results: "I want to say that one of the great features of America is that we have politician contests that they are very hard fought, as this one was hard fought, and once the decision is made, we unite behind the man who is elected. I want all of you to know I want Senator Kennedy to know and I want all of you to know that certainly if this trend does continue and he does become our next president, that he will have my whole hearted support and yours too. "
1964: Barry Goldwater vs Lyndon Johnson, Johnson won
"I have no bitterness. No rancor at all. I say to the president as a fellow politician, that he did a wonderful job. He put together a vote total that is larger than has ever been gained in this country," Goldwater said.
He further added: "I have sent the president the following wire which I think will be available for you if you don't have it now: 'To President Lyndon Johnson in Johnson City, Texas. Congratulations on your victory. I will help you in any way I can toward achieving a growing and better America, and a securer and dignified peace.'"
1968: Hubert H Humphrey vs Richard Nixon, Nixon won
"I am sure you all already know that I have called Mr Nixon to express to him our congratulations. And I have sent the following telegram just a few moments ago to Mr Nixon," Humphrey said.
"It reads as follows: 'According to unofficial returns, you are the winner in this election. My congratulations. Please know that you will have my support in unifying and leading the nation. This has been a difficult year for the American people. I am confident that if constructive leaders of both our parties join together now, we shall be able to go on with the business of building the better America we all seek, in the spirit of peace and harmony. Signed, Hubert H Humphrey'"
1972: George McGovern vs Richard Nixon, Nixon won his second term
"Congratulations on your victory. I hope that in the next four years you will lead us to a time in peace abroad and justice at home. You have my full support in such efforts. With best wishes to you and your gracious wife, Pat. Sincerely George McGovern."
1976: Gerald Ford vs Jimmy Carter, Carter won
Betty Ford on Behalf on Gerald Ford gave the speech: "The president asked me to tell you that he telephoned President-elect Carter a short time ago and congratulated him on his victory. The president also wants to thank all those thousands of people who worked so hard on his behalf and the millions who supported him with his votes."
"It has been the greatest honour of my husband's life to have served his follow Americans during two of the most difficult years in our history. The President urges all Americans to join him in giving your united support to President-elect Carter as he prepares to assume his new responsibilities," he added.
1980: Jimmy Carter vs Ronald Reagan, Reagan won
"The people of United States have made their choice, and of course I accept that decision," a shaky Carter read.
"I have a deep appreciation for the system, however, that lets people make the free choice about who will lead them for the next four years. About an hour ago I called Governor Reagan in California and I told him that I congratulated him for a fine victory. I look forward to working closely with him during the next few weeks. We will have a very fine transition period. I told him I wanted the best one in history."
"And then I sent him this telegram and I will read it to you: 'It is now apparent that the American people have chosen you as the next president. I congratulate you and pledge to you our fullest support and cooperation in bringing about an orderly transition of government in the weeks ahead. My best wishes are with you and your family as you undertake the responsibilities that lie before you and I signed it as Jimmy Carter.'"
1984: Walter Mondale vs Ronald Reagan, Reagan won his second term
"We rejoice in the freedom of a wonderful people and we accept their verdict. I thank the people of America for hearing my case. My loss tonight does not in any way diminish the worth or the importance of our struggle and I am at peace with the knowledge that I gave it everything I got. "
1988: Michael Dukakis vs George H Bush, Bush won
"Just a few minutes ago, I called Vice-President Bush and congratulated him on his victory. And I know I speak for all of you and for all the American people when I say that he will be our president and we will work with him. This nation faces major challenges ahead and we must work together. "
1992: Bush H Bush vs Bill Clinton, Clinton won
"I just called Governor Clinton over in Little Rock and offered my congratulations. He did run a strong campaign. I wish him well in the White House, and I want the country to know that our entire administration will work closely with his team to ensure the smooth transition of power."
"There is important work to done and America must always come first. So we will get behind this new president and wish him well. "
1996: Bob Dole vs Bill Clinton, Clinton won his second term
"I have said it repeatedly in this campaign that the president is my opponent not my enemy, and I wish him well and I pledge my support and whatever advances the cause of a better America. That's what the race was about in the first place, a better America as we go into the next century."
2000: Al Gore vs George W Bush, Bush won
"For the sake of our unity as a people and the strength of our democracy, I offer my concession," Gore said.
"Almost a century and half ago, Senator Stephen Douglas told Abraham Lincoln, who had just defeated for presidency: 'Partisan feeling must yield to patriotism. I am with you Mr President and God bless you.' Well, in that same spirit, I say to President-elect Bush that what remains of partisan rancor must now be put aside, and may god bless his stewardship of this country."
"Neither he nor I anticipated this long and difficult road. Certainly neither of us wanted it to happen. Yet it came and now it has ended. Resolved as it must be resolved, through the honored institutions of our democracy. "
2004: John Kerry vs George Bush, Bush won his second term
"Today, I hope we can begin the healing," Kerry remarked in his speech.
"I am sorry that we got here a bit late and a little bit short. Earlier today, I spoke to President Bush and offered him and Laura our congratulations on their victory. We had a good conversation and we talked about the danger of division in our country and the need, the desperate need for unity, for finding the common ground, coming together. Today I hope we can begin the healing"
2008: John McCain vs Barack Obama, Obama won
"Whatever our differences, we are fellow Americans and please believe me when I say: No association has ever meant more to me than that," said an emotional McCain.
"This is a historic election and I recognize the special significance it has for African Americans and for the special pride that must be theirs tonight. I have always believed that America offers opportunities to all who have the industry and will to seize it. "
"Senator Obama believes that too. But we both recognize that though we have come a long way from the old injustices that once stained our nation's reputation and denied some Americans the full blessings of American citizenship, the memory of them still had the power to wound," McCain remarked.
"A century ago, President Theodore Roosevelt's invitation pf Booker T Washington to dine at the White House was taken as an outrage in many quarters. America today is a world away from the cruel and prideful bigotry of that time. There is no better evidence of this than the election of an African-American to the presidency of the United States."
2012: Mitt Romney vs Barack Obama, Obama won his second term
"I have just called President Obama to congratulate him on his victory. His supporters and his campaign also deserve congratulations. I wish all of them well, but particularly the president, the first lady and their daughters. I so wish that I had been able to fulfil your hopes to lead the country in a different direction. But the nation chose another leader. And so Ann and I join with you to earnestly pray for him and for this great nation."
2016: Hillary Clinton vs Donald Trump, Trump won
"I still believe in America and always will. And if you do, then we must accept this result and then look to the future. Donald Trump is going to be our president. We ow him an open mind and a chance to lead. Our constitutional democracy enshrines the peaceful transfer of power. And we don't just respect that, we cherish it."
2020: Donald Trump vs Joe Biden, Biden won
Donald Trump refused to formally concede the US election, even as senior Republicans began to distance themselves from him, and as recriminations were reported among aides to a man doomed to go down as an impeached, one-term president.
Before the race was called, Trump continued to tweet his defiance and to attract censure for making baseless claims about voter fraud and his supposed victory.
"The simple fact is this election is far from over," Trump insisted.
"Joe Biden has not been certified as the winner of any states, let alone any of the highly contested states headed for mandatory recounts, or states where our campaign has valid and legitimate legal challenges that could determine the ultimate victor."