This was a simple message that cut straight to the core of the argument on Europe and with which a large section of the population could identify. It was politically clever, easy to remember and, above all, simple and straightforward.
It was key to the success of the campaign.
Since entering Government, however, Mr Cummings appears to have lost sight of these principles of campaigning success and, far from taking back control of the agenda, it appears that the Government has in recent weeks lost control of the narrative and the ability to shape events.
He began well in early August as the Government began to roll out a series of retail policy announcements on police funding and law and order, the NHS and Schools – all clearing the decks for a general election by appealing to the voters whom the Tories would target at the polls.
This strategy appeared to be working as the Tories began to climb in the polls to north of 30 per cent while Labour (with whom they had been on level pegging in June) languished at about 20 per cent.
Then, in late August, a series of things started to go awry.
What should have been a great media win for the Prime Minister, with Johnson making a speech in front of a cohort of new police officers, turned into a negative as it emerged that his team had not done the simple courtesy of clearing with the Police that the Prime Minister would make a political speech in front of them.
It was an avoidable error and demonstrated a lack of due diligence and disregard for precedent and normal etiquette that now appears to be part of a pattern.
This pattern included, most notably, the now non-prorogation of Parliament, the briefings against the Supreme Court, and the expulsion of 21 hitherto loyal Conservative MPs for voting against the Government Whip – an act of self-harm which deprived the Government of its own majority and ensured its subsequent defeats in Parliament by the Benn Bill.
The consequences of all of this are a Prime Minister who had to cut short his trip to New York to attend Parliament, and a Government devoid of a majority, unable to determine its own agenda and unable to call an election.
The Government has now essentially sabotaged its own party conference, which will now most likely take place as Parliament sits.
It is difficult to imagine that this is, or was, all part of Mr Cummings' grand plan.
By mid-August it had become clear that Mr Cummings himself was increasingly becoming the story.
He gave curbside briefings to the media outside his home, breaking all precedent for advisers, and was the subject of newsreels as his brutal management of staff in CCHQ came to light.
The much-publicised 'defenestration' of Sajid Javid’s SpAd without the Chancellor's prior knowledge or consent has become typical of Cummings' tenure.
Since then we have seen a pattern of strategic blunders in government strategy and communications, characterised by hasty action and hubris.
These actions have often led to either acts of self-harm, leading to forced U-turns, loss of control of the agenda and narrative or, at the very best, Pyrrhic victories.
The key thing to note is that these machinations and mis-steps have played badly with those of us inside the 'London media bubble', as Cummings would have it.
However, the true test will be the coming election.
We will know if he has succeeded only when we see how his mantra of "get out of London" plays with the new target voter base.
His tenure in Downing Street will be entirely dependent on that test and that test alone, regardless of what anyone else may think.
Stephen Day is head of international issues and campaigns for FTI consulting
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