WATCH: Expert fact-checker explains Trump’s worst lie of 2018 — so far

MSNBC anchor Nicolle Wallace dedicated the first two segments of "Deadline: White House" on Christmas Eve to examining President Donald Trump's pattern of lying to the American people.

"Donald Trump lies with the velocity that's hard to keep track of," Wallace noted. "Beyond the frequency of the lies are serious issues and the grave disservice that the president does by conditioning the public to expect so little from their public servants."

For analysis, Wallace interviewed Toronto Star Washington correspondent Daniel Dale, who has been widely praised for his efforts to fact-check every single lie from the commander-in-chief.

"We've been talking about the behavior of lying, the pattern of lying," Wallace noted. "But I want to dig deeper into the consequences of lying."

"He's been lying without consequence for decades, to the tabloids, to the entertainment press, to Congress, to voters," Dale noted.

"He even called and pretended to be his own publicist -- he even lied about who he was," Wallace interjected.

Dale went through some of Trump's dishonesty that he considered when deciding upon the top lie of 2018.

Dale declared Trump's top lie was that he did not know about the hush-money payment to Stormy Daniels.

"This is a big deal because this is the president lying about a crime," Dale concluded. "Michael Cohen has pleaded guilty to felonies over this -- these payments that the president has lied about and now the president himself faces legal jeopardy over it."

"And so there's so much silliness -- lies about crowd sizes -- you know, so much we can laugh at, but this is really serious stuff here," he added.

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