oris Johnson once cited his favourite movie scene as the multiple retribution killings at the end of The Godfather. But it’s a line from the film’s sequel that best explains the events that have led to the row between the prime minister and his former adviser Dominic Cummings that is currently engulfing Downing Street: “Never hate your enemies. It affects your judgment.” On Thursday, Downing Street briefed several newspapers that Johnson believed his one-time right-hand man had been behind a number of damaging government leaks. These leaks were wide-ranging – from the recent publication of messages between Johnson and James Dyson over ventilators, to the leaked news of England’s second lockdown, when Johnson was forced to bring forward plans for a circuit breaker. Since Cummings quit, following a row that included Johnson’s fiancee, Carrie Symonds, the relationship between the prime minister and his former aide has gone from bad to worse. Aides have been advised against keeping in contact with members of the Vote Leave team, and Johnson has seemed keen to remove all reminders of Cummings from Downing Street. Johnson’s belief that damaging stories in the papers – from the Downing Street refurbishment, to Dilyn the dog’s antics and his messages to the Saudi crown prince Mohammed bin Salman – were down to Cummings have compounded these tensions. Aides argue that Cummings is “bitter” that the government hasn’t fallen down in his absence. What the briefings last week did, however, was to make a private annoyance public. Cummings was quick to hit back with a blog post in which he denied being the source of the leaks and made new allegations, claiming the prime minister considered breaking the law with his plans for a lavish Downing Street flat refurbishment, and that he called off a leak inquiry because he was concerned it could mean he had to fire one of his fiancee’s close friends. Given the Tories are currently riding high in the polls, one could be forgiven for thinking this is a court drama that will simply fizzle out. But understanding the row is important, because it could have big implications for the government. Why did the prime minister decide to go on the attack? There are two schools of thought about the wisdom of this approach. The charitable case, as put forward by Johnson’s most loyal supporters, is that he was simply responding to a campaign of abuse from Cummings and this was the best way to limit the damage. The reasons for this are twofold. One, Cummings is not a popular public figure. The row over his trip from London to Durham during England’s first lockdown made him one of the most unpopular figures in the country. Even to this day, “red wall” MPs say that wordclouds of constituent emails show “Barnard Castle” in the largest font. It follows that as Johnson is more popular than Cummings, blaming the former aide could limit the damage to his public reputation. The second reason is 26 May – the date that Cummings is due to give evidence to MPs about the government’s Covid response. There are nerves in No 10 ahead of this appearance, particularly about what Cummings could say and what evidence he could later provide. “I wouldn’t be surprised if he made a load of outlandish claims, forced the government to deny them and then published all the evidence,” says one former colleague of Cummings. If the prime minister were successful in discrediting Cummings as a figure ahead of this appearance, some think it could limit the damage. This is why the leak of England’s second lockdown is particularly significant. Cummings denies it was him. Were the prime minister able to prove otherwise, it could make his former aide appear an unreliable witness. Yet few people have made these arguments. Even if discrediting Cummings was Johnson’s aim, it seems odd that he would have triggered this row before a bumper set of local elections, rather than waiting until after polling day. Speak to government aides and MPs who support the prime minister and they are more likely to say this is all a horrible misjudgment. “A lot of people were saying this is a massive mistake, but the prime minister just cracked,” says one government figure. “It was death by a thousand cuts. He’s not a happy figure.” The fear is that Johnson has fallen into a trap – a public spat he cannot win. It’s not that Johnson won’t damage Cummings, but rather that Johnson simply has far more to lose. One is a public figure keen for re-election in a few years’ time, the other is a private individual. For now, however, Johnson has the support of his parliamentary party. Many Tory MPs were desperate to see the back of Cummings – he had little time for them when in post. While the current headlines are far from ideal, the more important thing is that MPs do not believe this row will affect the local elections. The Tories are still enjoying a comfortable lead in the polls. Although Labour has been going on the attack on Tory sleaze since the Greensill saga, MPs say it appears to have had little impact on the doorstep so far. Several Conservative MPs claim they have not received a single email from constituents over Greensill and lobbying. But this could change. MPs returning to parliament this week after a weekend out on the doorstep say constituents have started to voice the issue of the flat refurbishment, along with Tory infighting. If these become contentious issues among voters, Tory nerves will grow. Johnson didn’t win the support of his party because he has close individual ties within it. In fact, he doesn’t have much in the way of a loyal camp of MPs. What keeps him in place is the fact that he is viewed as a winner. If the Cummings row changes this, the prime minister will have a real reason to worry. Katy Balls is the Spectator’s deputy political editor