For all his inconstancy of character, Donald Trump is a master manipulator. He rose to political prominence by slandering Barack Obama. He rode the birther myth as far as it would go – before brazenly jettisoning it with the insistence that it was all the handiwork of Hillary Clinton.

Now once again, he seeks to buoy his political fortunes by attacking Obama. Perhaps what is so striking about the tweets is not their desperation, but their cynicism. In exclaiming “This is McCarthyism!”, Trump said something deeply revealing – only about himself. McCarthyism was never in the first instance about wiretapping. It was about defaming public officials with charges of treason without a shred of evidence. Sounds familiar, no?

Equally revealing was Trump’s tweet: “I’d bet a good lawyer could make a great case out of the fact that President Obama was tapping my phones in October, just prior to Election!” As Trump well knows, a good lawyer can make a case out of anything.

In the 1970s, after the justice department accused the Trump Corporation of racially discriminatory rental policies, Trump hired Roy Cohn. This was a man who, as a young lawyer, had assisted Joseph McCarthy’s red-baiting. On Trump’s behalf, Cohn countersued the government for $100m, a tactic Trump absorbed and has practiced throughout his career: when on the defensive, attack.

Concerned about congressional investigations into contact between his campaign and the Russians? Make a groundless charge of wiretapping against Obama and insist that the allegations be included in the investigations.

Cohn’s countersuit did not prevail, nor will Trump’s charges against Obama stick. But that is not the point. The point is to distract attention away from real allegations by creating a chaos of conflicting claims. And in this regard the strategy is all too effective. If there is something extraordinary about Trump it is how low he is willing to go.

Trump spokeswoman Sarah Huckabee was undoubtedly correct when she observed that “if this [the wiretapping] happened … we have … seen … a huge attack on democracy itself.” But if it didn’t, we have witnessed an attack on democracy no less ominous. It is an attack at once concerted and ongoing.

It’s hard to know where it goes from here. Perhaps Trump will turn his attention to a more traditional enemy: not a perceived political rival but a nation allegedly threatening American interests. Not an Australia, but a North Korea or Iran or even China. No better way to drown the voices of dissent than by pounding the martial tattoos of the war drum. Or maybe he will continue to tilt at his fellow Americans.

Since his inauguration a scant six weeks ago, Trump has defamed a great newspaper, a federal judge, and a former president. He has attacked whole institutions, pillars of American democracy. He appears willing to hold a great constitutional order hostage to his narcissism and political insecurities.

One wishes to echo the words of Joseph Welch who famously asked of Joe McCarthy: “Have you no sense of decency, sir? At long last, have you left no sense of decency?”

