As president, Donald Trump could be undone by untruths. He ran a successful campaign laced with lies, but he cannot run the country that way.

Finding workable solutions to policy problems requires a common understanding of what the problems actually are. Facts, not fabrications, fuel the governing process.

News reporters and fact-checkers tried aggressively to call out Trump's falsehoods during the campaign, but those efforts made little impact on his true believers. The new president's former adviser Corey Lewandowski practically laughed at the media's obsession with facts, telling them at a Harvard panel last week: "You guys took everything that Donald Trump said so literally. The American people didn't. They understood it."

"What we missed is that nobody cared about solutions," added Sarah Huckabee Sanders, who ran her father, Mike Huckabee's, campaign before joining Team Trump. "They just wanted to burn it all down. They didn't care about building it back up."

Trump's devotion to duplicity was reinforced by an epidemic of "fake news": deliberately false stories designed to damage Hillary Clinton -- and make money for the hucksters who exploited the open arms and closed minds of many Trump backers.

"Fake news," writes media critic Neal Gabler, "is an assault on the very principle of truth itself: a way to upend the reference points by which mankind has long operated. You could say, without exaggeration, that fake news is actually an attempt to reverse the Enlightenment."

This flood of falsity might have altered the election. We can't be sure. But we can be sure of this: Fakery won't work as a basis for governing.

As his presidency comes to a close, President Obama has been reflecting on the perils of policymaking in the age of social media. As he told David Remnick of The New Yorker, the new media ecosystem "means everything is true and nothing is true." The traditional gatekeepers that defined and described reality -- academics, journalists, scientists -- are easily bypassed and undermined. As a result, said Obama, it's "very difficult to have a common conversation," which is exactly what effective legislating requires.

The current situation marks "a decisive change from previous eras," reports Remnick, who quotes the president at length: "Ideally, in a democracy, everybody would agree that climate change is the consequence of man-made behavior, because that's what 99 percent of scientists tell us. And then we would have a debate about how to fix it.

"That's how, in the '70s, '80s and '90s, you had Republicans supporting the Clean Air Act and you had a market-based fix for acid rain rather than a command-and-control approach. So you'd argue about means, but there was a baseline of facts that we could all work off of. And now we just don't have that."

Trump's post-election behavior has not been encouraging. He took to Twitter to claim -- with absolutely no evidence -- that millions of illegal ballots deprived him of victory in the popular vote. And he's displayed a paper-thin skin, ranting against anyone who dares to criticize him, from established media outlets to the casts of "Hamilton" and "Saturday Night Live."

His supporters have made some truly astounding -- and disturbing -- claims. One of them, Scottie Nell Hughes, said on NPR, "People that say 'facts are facts' -- they're not really facts. ... There's no such thing, unfortunately, anymore, as facts." To "a certain crowd," Trump's core loyalists, his tweets "are truth." He alone is the Monarch of Meaning, the Arbiter of Accuracy.

But Hughes is dead wrong. As Obama likes to say, "Reality has a way of asserting itself." Or as an earlier president, John Adams, famously put it in 1770, "Facts are stubborn things; and whatever may be our wishes, our inclinations or the dictates of our passion, they cannot alter the state of facts and evidence."

Obama has struck a cautiously hopeful note. As he told a White House press conference after meeting with Trump, "Regardless of what experience or assumptions he brought to the office, this office has a way of waking you up."

But he also warned Trump that "campaigning is different from governing. ... Because when you're a candidate and you say something that is inaccurate or controversial, it has less impact than it does when you're president of the United States. Everybody around the world is paying attention."

Yes, they are. John Adams was right 246 years ago, and he's right today. You can burn the government down with lies, but you can only build it up with facts. And unless Trump recognizes that truth, his presidency is doomed.