Former Presidents Barack Obama and George W Bush have voiced concern about the current political climate in the US, in comments seen as a veiled rebuke of Donald Trump's leadership.
Obama urged Americans to reject the politics of "division" and "fear", while Mr Bush criticised "bullying and prejudice" in public life.
Both were speaking separately; neither mentioned President Trump by name.
Trump, who has been critical of his two predecessors, is yet to comment.
Ex-presidents traditionally shy away from the political stage, and it was long considered in poor taste for a former occupant of the Oval Office to criticise one of his successors, the BBC's North America reporter Anthony Zurcher says.
But norms and standards of behaviour that once seemed to be set in stone have fallen by the wayside in the current political environment, our reporter adds.
Speaking at a Democratic campaign event in Newark, New Jersey, Mr Obama said Americans should "send a message to the world that we are rejecting a politics of division, we are rejecting a politics of fear".
He added: "What we can't have is the same old politics of division that we have seen so many times before that dates back centuries.
"Some of the politics we see now, we thought we put that to bed. That's folks looking 50 years back. It's the 21st Century, not the 19th Century. Come on!"
He touched on similar themes at another event later in Richmond, Virginia, saying: "We've got folks who are deliberately trying to make folks angry, to demonise people who have different ideas, to get the base all riled up because it provides a short-term tactical advantage."
Speaking just hours earlier in New York, Mr Bush said: "Bigotry seems emboldened. Our politics seems more vulnerable to conspiracy theories and outright fabrication.
"There are some signs that the intensity of support for democracy itself has waned - especially among the young."
Americans, he said, have "seen our discourse degraded by casual cruelty".
"At times it can seem like the forces pulling us apart are stronger than the forces binding us together.
"We've seen nationalism distorted into nativism, forgotten the dynamism that immigration has always brought to America."