While presidents have been at odds before, there is often a sort of camaraderie among the small club of individuals who have served in the highest office in the land.

Barack Obama urged Americans to resist President Donald Trump’s bullying. Joe Biden warned that Trump is wrecking the “sacred promise” of Social Security. Bill Clinton decried the emphasis on grievances and the need to dominate.

In an extraordinary stretch of just over two weeks, three former presidents have taken to the public stage to sound the alarm against the current occupant of the White House, despite the tradition that former presidents generally refrain from publicly criticizing their successors.

Obama, Biden and Clinton did not explicitly name Trump, but their message was unmistakable. The three Democrats said, as much by their presence as their words, that these are unusual times for American democracy, that norms are being disregarded and extraordinary measures are required. The only living president who has not spoken out since Inauguration Day is Republican George W. Bush, though he has made little secret of his antipathy for Trump.

“Former presidents are uniquely qualified and situated to raise their voices and warn the American people if the country is taking a dangerous turn,” said Timothy Naftali, a historian at Columbia University’s School of International and Public Affairs. “Think of them as a sort of advisory council to the people of the United States. And when the advisory council sounds the alarm, the people should listen.” Biden, speaking in Chicago on Tuesday at the national conference of Advocates, Counselors and Representatives for the Disabled, denounced Elon Musk’s cuts to Social Security, his first public remarks since leaving office. “The last thing [beneficiaries] need from their government is deliberate cruelty,” Biden said, adding, “In fewer than 100 days, this administration has done so much damage and so much devastation.”

Clinton spoke at an emotional ceremony in Oklahoma City on Saturday morning to commemorate the bombing 30 years ago of the Alfred P. Murrah Federal Building, which killed 168 people. Clinton compared the way that city has come together with the current national divisions.

“It’s like everybody is arguing about whose resentments matter most, whose resentments are more valid, when it’s okay to stretch the truth a little bit to gain an advantage,” Clinton said. “If our lives are going to be dominated by the effort to dominate the people we disagree with, we are going to put the 250-year march to a more perfect union at risk.”

Clinton praised the service of federal workers at a time when Trump is slashing the federal workforce. He also made a case for humility. “It does you good every now and then to admit you’re wrong,” he said.

It is unusual for a single president to publicly excoriate his successor, historians say, given the American tradition of seamless transfers of power and the principle that the country has one president at a time. For three to do so in such short order may be unprecedented.

“What is really significant is this is happening before the end of the first 100 days of the Trump presidency,” Naftali said. “Ordinarily, former presidents give the current president space to establish himself and learn the rules of the road. … But these presidents already see the contours of the changes that President Trump wishes to bring.”

The White House did not immediately respond to a request for comment.

The three Democratic presidents spoke in terms of fundamental American traditions and values. But their relationship with Trump is also marked by personal animosity, as Trump has aimed attacks and insults at each of them or their family members.

He has repeatedly mocked “Sleepy Joe” Biden as a senile, elderly figure who has no idea what he is saying much of the time. Three months into his second term, Trump continues to regularly disparage Biden.

After Biden defeated him in 2020, Trump falsely claimed the election was stolen, an assertion he still clings to. He has attacked Biden’s son Hunter as a criminal and drug addict, recently ending Secret Service protection for Hunter and Biden’s daughter Ashley. (Hunter acknowledges spiraling into addiction after the death of his brother, Beau.)

Caption of Picture-   Presidents

Presidents Bill Clinton, George W. Bush, Barack Obama, Donald Trump and Joe Biden at the funeral of their predecessor Jimmy Carter in January.