In the end, Michael Cohen’s claim that he would “take a bullet” for Donald Trump proved as hollow as many of the other boasts he once made about his relationship with the president.

In return for a reduced prison term, Mr Trump’s long-standing personal lawyer and fixer this week pleaded guilty to a string of tax and campaign law offences and pointed a finger squarely at the president.

Ominously for Mr Trump, those violations related to the 2016 race are neither archane nor incomprehensible to the wider public.

Instead Mr Cohen, once described as Mr Trump's “Jewish wingman”, admitted that he paid hush money to two women — Playboy model Karen McDougal and porn star Stormy Daniels — to stop details of their alleged affairs with the president breaking before election day.

He did so, Mr Cohen declared in court, “in coordination with and at the direction of” the then Republican presidential candidate.

The news provoked headlines not seen since the days of Watergate. In an editorial the morning after Tuesday’s dramatic developments, the Washington Post declared Mr Trump to be “an alleged co-conspirator in the White House”.

Analysts believe that there will be no immediate legal consequences for Mr Trump. The Justice Department has long believed that presidents cannot be charged with a crime.

But the implications could be politically dire. If the Democrats retake control of the House of Representatives in this November’s mid-term elections they are sure to launch investigations into this, and a multitude of other scandals swirling around the Trump White House.

Impeachment proceedings and an effort to remove the president from office could then follow, although the Democrats might conclude that their chances of defeating Mr Trump in 2020 might be best served by leaving him gored and bleeding in the Oval Office.

Steve Schmidt, a Republican political strategist who quit the party earlier this year in disgust at the president’s behaviour, suggested: “The bill is coming due for Trump with regard to his many years of lawlessness and arrogance.”

The president’s public silence on his lawyer’s court appearance spoke volumes. There were no angry Tweets and no public flailing of Mr Cohen, although Mr Trump is said to have privately raged for months that his former lawyer is not “smart or loyal” and he wanted to see him destroyed.

The reason is not hard to discern. Mr Trump is all too aware of just how many of his business and political secrets his former consigliere knows.

In a none-too-subtle hint at that, Mr Cohen’s lawyer Lanny Davis — by delicious irony, a one-time adviser to Bill Clinton — told the media that his client has information which would be of “a great deal of interest” to special counsel Robert Mueller.

Mr Davis suggested Mr Cohen was happy to discuss topics including the “computer crime of hacking” and “whether or not Mr Trump knew ahead of time about that crime and even cheered it on” with Mr Mueller, who is probing Russian interference in the 2016 election.

Facing this potentially existential threat, Mr Trump’s propensity to lash out and his instinct for self-preservation will increasingly be at odds. Few would bet on the latter prevailing.