Story highlights John McTernan: Trump is like the arsonist who sets fire to your house, then offers to help

Trump hailed as modern-day Demosthenes for modestly competent speech, he says

John McTernan is a former speechwriter for ex-British Prime Minister Tony Blair and ex-communications director to former Australian Prime Minister Julia Gillard. The opinions expressed in this commentary are his.

(CNN) In politics, language is a legacy. Politicians who understand this employ great speechwriters and pay close attention to the words that they use.

Think of Ted Sorensen's work for President John F. Kennedy or Peggy Noonan's for President Ronald Reagan . They produced linguistic tropes and passages that echo down the decades. Their language still inspires and reminds us that if the presidency is, in Teddy Roosevelt's words, a "bully pulpit," it can, like all pulpits, be a source of lasting inspiration and optimism.

President Donald Trump, too, has become known for his language -- but for a very different reason. His stump speeches on the campaign trail were famously rambling and unstructured.

His main method of communication both as a candidate and as President has been Twitter . The 140-character form has produced many phrases that have since passed into common usage such as "sad!" and "fake news." Poetic phrases that will be an inspiration for the ages, these are not.

The incoherence of the campaign trail followed Trump into the presidency, mutating into what was virtually a self-parody -- see the epic press conference where he answered all questions with the depth of his own tweets.

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