Timothy Stanley is a historian and columnist for Britain's Daily Telegraph. He is the author of "Citizen Hollywood: How the Collaboration Between LA and DC Revolutionized American Politics." The opinions expressed in this commentary are his.

(CNN) A new CNN poll shows Donald Trump being easily beaten in 2020 by three potential Democratic nominees. Joe Biden is ahead 57-40%. Bernie Sanders by 55-42%. Oprah Winfrey by 51-42%.

Timothy Stanley

Should the President panic? No. Trump has a history of coming from behind and surprising us, and by 2020 he hopes to have accumulated a raft of real accomplishments to beat his opponents with.

So how are we to receive the news of this poll?

To begin with, we need a new rule when it comes to discussing Donald Trump: He won in 2016, get over it.

Constant debate about how he did it or what it says about America is redundant. In fact, this rehashing works to his advantage, not only because it winds up liberals to the point of madness, but because it focuses conversation on the point in history when he was probably at his most popular.

Read More