Former President Barack Obama said “strongman politics are ascendant,” delivering a rebuke to his successor Donald Trump, without mentioning him by name.

“Look around. Strongman politics are ascendant, suddenly, whereby elections and some pretense of democracy are maintained, the form of it, but those in power seek to undermine every institution or norm that gives democracy meaning,” he said in a speech in South Africa to mark the 100th anniversary of Nelson Mandela’s birth.

Obama said “a politics of fear and resentment and retrenchment began to appear and that kind of politics is now on the move.”

“It’s on a move at a pace that would have seemed unimaginable just a few years ago,” he said. “I’m not being alarmist. I’m simply stating the facts.”

His speech came one day after Trump declined to condemn Russian President Vladimir Putin, despite the assessment of U.S. intelligence agencies that Russia interfered with the 2016 presidential election by hacking computer systems and using other tactics. He appeared to accept Putin’s denial that he had anything to do with it.

Obama has occasionally weighed in on some of Trump’s actions, like his decision to abandon the Paris climate accord and the Iran nuclear deal. But he has used his platform as a former president sparingly, something that could change as the midterms approach.

He decried the brand of Trump’s politics that has overtaken much of the Republican party, including “far-right protectionism and closed borders, but also on barely hidden racial nationalism.”

But he also warned of the impact that “strongman politics” is having on democratic institutions, like the press. He also criticized what he called the “utter loss of shame among political leaders, where they’re caught in a lie and they just double down and lie some more.”

“You have to believe in facts. Without facts, there’s no basis for cooperation. If I say this is a podium and you say this is an elephant, it’s going to be hard for us to cooperate,” Obama said.

He offered a work of hope amid the “strange and uncertain times we are in,” putting the pressures on western democracies in perspective.

“We’ve been through darker times,” he said. “We’ve been in lower valleys. Yes, by the end of this life, Madiba embodied the successful struggle for human rights. But that journey was not easy. The man went to prison for almost three decades.”