NEW YORK -- Americans are facing an "epidemic of dishonesty" in Washington that's more dangerous than terrorism or communism. That's according to former New York City Mayor Michael Bloomberg, who warned in a commencement speech on Saturday at Texas' Rice University that "an endless barrage of lies" and a trend toward "alternate realities" in national politics pose a dire threat to U.S. democracy.

The 76-year-old billionaire, who flirted with an independent presidential run in 2016, did not call out any politicians by name.

Although he derided Donald Trump as "a con" and a "dangerous demagogue" before his election, in an interview before the speech Bloomberg refused to comment specifically on the Republican president's troubled history with the truth. Fact checkers have determined that Mr. Trump has made hundreds of false and misleading statements since entering the Oval Office.

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"This is bigger than any one person. It's bigger than any one party," he said in the interview.

In the speech, Bloomberg evoked the legend of the nation's first president, George Washington, who as a boy said he could not tell a lie when asked if he cut down a cherry tree.

"How did we go from a president who could not tell a lie to politicians who cannot tell the truth?" Bloomberg asked Rice graduates and their families gathered in Houston.

He blamed "extreme partisanship" for an unprecedented tolerance of dishonesty in U.S. politics. People are committed more to their political tribes than the truth, he said, suggesting that the nation is more divided than any time since the Civil War.

"There is now more tolerance for dishonesty in politics than I have seen in my lifetime," Bloomberg said. "The only thing more dangerous than dishonest politicians who have no respect for the law is a chorus of enablers who defend their every lie."

For example, he noted that Democrats spent much of the 1990s defending President Bill Clinton against charges of lying and personal immorality just as Republicans attacked the lack of ethics and honesty in the White House. Just the reverse is happening today, he said.

In one jab at Mr. Trump, he noted that the vast majority of scientists agree that climate change is real. Mr. Trump and his Republican allies have repeatedly called climate change a hoax promoted by America's adversaries.

"If 99 percent of scientists whose research has been peer-reviewed reach the same general conclusion about a theory, then we ought to accept it as the best available information -- even if it's not a 100 percent certainty," Bloomberg said. He added: "That, graduates, is not a Chinese hoax."

He warned that such deep levels of dishonesty could enable what he called "criminality." Asked what specifically he was talking about, Bloomberg noted "lots of investigations" going on, but he declined to be more specific.

Several Trump associates are facing criminal charges as part of a federal probe into Russia's meddling in the 2016 election. Three have already pleaded guilty to making false statements to the FBI. Federal investigators want to interview Mr. Trump himself, although the president's legal team has resisted so far.

"When elected officials speak as though they are above the truth, they will act as though they are above the law," Bloomberg told Rice graduates. "And when we tolerate dishonesty, we get criminality. Sometimes, it's in the form of corruption. Sometimes, it's abuse of power. And sometimes, it's both."

Bloomberg wasn't the only commencement speaker to discuss a culture of untruths this week. On Friday, Oprah Winfrey encouraged graduates of the University of Southern California's (USC) Annenberg School for Communication and Journalism to keep people who disparage news as "fake" in check.

"You are in a position to keep all those who now disparage real news, you are going to be the ones who keep those people in check. Why? Because you can push back and you can answer false narratives with real information. You can set the record straight," Winfrey said. "You also have the ability and power to give voice who desperately now need to tell their stories and have their stories told."

Winfrey encouraged graduates to challenge those from the political left, right and center, holding them accountable.

"When you see something, say something. And you say it with the facts and the reporting to back it up," she said. "You make the choice everyday to exemplify honest because the truth exonerates and it convicts, it disinfects and it galvanizes. The truth has always been, and will always be, our shield against corruption, greed and despair -- the truth is our saving grace."