Every good controversy gets a 'gate'.

It all started with 'Watergate' in the 1970s but since then, countless scandals have been anointed with the suffix.

'Bridgegate' refers to a scheme that intentionally caused traffic chaos in New Jersey in 2013 in order to punish a local mayor for failing to endorse the governor's re-election bid.

In Ireland recently, the term 'Printergate' was coined following the purchase of a very expensive, state-of-the-art printing press that was too large to fit inside Leinster House.

The latest 'gate' to enter political discourse in the US is 'Obamagate'.

What exactly the controversy is depends on who you talk to.

The term 'Obamagate' was first used by President Donald Trump and, as the name suggests, it involves some sort of scandal linked to his predecessor Barack Obama.

Although he invented the concept, Mr Trump was not able to shed much light on exactly what wrongdoing he was accusing Mr Obama of when he was asked about it recently by reporters.

"Obamagate. It's been going on for a long time. It’s been going on from before I even got elected. And it’s a disgrace that it happened," he said.

When pressed by journalists to name the specific criminal offence, Mr Trump replied: "You know what the crime is. The crime is very obvious to everybody."

The problem is, it's not that obvious.

Donald Trump's supporters and conservative media commentators have latched onto 'Obamagate' as a vague conspiracy theory linked to a "deep state" attempt to destroy the Trump presidency just before Barack Obama left office.

In recent weeks, Mr Trump has posted hundreds of tweets and retweets about this alleged wrongdoing.  Many of the messages contain links to articles which, the US president claims, offer proof of what he has described as "the biggest political crime in American history".

"People should be going to jail for this stuff," Mr Trump said in an interview with the Fox Business Network.

"This was all Obama, this was all Biden. These people were corrupt, the whole thing was corrupt, and we caught them."

Michael Flynn

At the core of the 'Obamagate' controversy is Donald Trump's first National Security Adviser, Michael Flynn.

General Flynn pleaded guilty to lying to the FBI about his dealings with the Russian ambassador to the US in the weeks after Donald Trump won the 2016 election.

Earlier this month, US Attorney General William Barr announced that the Justice Department was dropping its case against Michael Flynn, because it was no longer convinced the FBI’s interview that underpinned the charges was conducted with a "legitimate investigative basis".

The Attorney General said his department did not think General Flynn's statements were "material even if untrue."

"Our duty we think, is to dismiss the case," William Barr told CBS News.

"A crime cannot be established here. They did not have a basis for the counterintelligence investigation against Flynn."

Michael Flynn's lawyers had argued that the FBI had intentionally tried to entrap their client by tricking him into lying.

His legal team pointed to recently released documents that appear to show investigators planning their interview strategy.

"What is our goal? Truth/admission or to get him to lie, so we can prosecute him or get him fired?" an unidentified person wrote in notes prepared ahead of Michael Flynn's FBI interview in January 2017.

The Flynn case was a central part of the Mueller Investigation into possible collusion between the Trump campaign and Russia.

When the Justice Department announced that the Flynn charges were being dropped, it added fuel to Donald Trump's claims that the entire Mueller probe had been a politically motivated witch-hunt.

"General Flynn was targeted by the Obama administration and he was targeted in order to try and take down a president, and what they've done is a disgrace," Mr Trump said.

Those spreading the 'Obamagate' theory claim that both Barack Obama and his Vice President Joe Biden had advance knowledge of the FBI's plans to interview Michael Flynn and were engaged in an effort to spy on the incoming Trump administration.

Unmasking 

Under US law, Americans' names discovered in foreign communication intercepts must be kept secret unless senior officials ask for them to be disclosed or "unmasked".

Earlier this month, a list was released of Obama administration officials who had sought to unmask Trump associates, including General Michael Flynn.

Among those who had made unmasking requests was former US Vice President Joe Biden.

This immediately led to claims by Donald Trump and his supporters that Mr Biden, and others within the Obama administration, had improperly and illegally exposed the identity of Michael Flynn.

The Washington Post reported on Wednesday however that General Flynn's name had never been "masked" in the first place.

Barack Obama 

Donald Trump is not running against Barack Obama in November's election, so why is he attacking him now?

One reason might be that Mr Obama has recently started to attack Mr Trump.

Since leaving the White House, Barack Obama had largely stayed out of politics and had avoided making public comments until now.

He re-entered the fray last month when he endorsed Joe Biden, but he has gone further of late, criticising the man who succeeded him in the White House.

In a leaked conversation with former staff members, Barack Obama described the US response to the coronavirus as anaemic and spotty.

"It would have been bad even with the best of governments. It has been an absolute chaotic disaster when that mindset - of 'what's in it for me' and 'to heck with everybody else' - when that mindset is operationalised in our government," he said.

In the days after those comments were reported, Donald Trump took to twitter to ramp up his references to 'Obamagate'.

Barack Obama went on the attack again last week.

In a virtual speech to high school graduates he spoke about grownups with fancy titles and important jobs behaving like children.

Donald Trump responded by calling his predecessor "an incompetent president."

"I think President Obama was one of the worst presidents in the history of our country," he said.

Another smokescreen?

Donald Trump's critics say the whole 'Obamagate' conspiracy theory is a smokescreen created by the US president to distract from his handling of the coronavirus pandemic.

Mr Trump is no stranger to distraction and deflection when he is coming under fire.

In recent weeks he has blamed the Covid-19 crisis on China, the World Health Organization and even the Obama administration, which he has accused of failing to prepare for such an outbreak.

Whether it is the Access Hollywood tapes, the Muller Investigation or impeachment, Donald Trump has survived controversies that would destroy most politicians.

His survival tactics have remained consistent throughout.

He frequently portrays himself as the victim who is under attack from the mainstream media and the political establishment.

He then turns the tables on his attackers accusing them of wrongdoing. It is a strategy that has worked in the past.

'Obamagate' is another political tactic by Donald Trump.

He is hoping that by highlighting this scandal he will generate a 'gate' a different kind; a floodgate that will open and engulf the Democrats in controversy ahead of November's election.