Many Conservative MPs would dump Boris Johnson in a flash if they could name the obvious successor. That is the wrong test. The replacement options become clear only once there is a vacancy, and obvious successors rarely succeed anyway. Westminster has buried many uncrowned dauphins. There are other questions the Tories should be asking themselves. One is how much the opposition wants Johnson to stay. A lot, is the answer. For as long as Downing Street is occupied by a man who broke the law and lied about it, the government’s message is corrupted. A dismal TV interview on Tuesday illustrated the problem. The prime minister had to begin by asserting his honesty, which is not something any politician can self-certify. He was then unable to summon plausible empathy for people feeling the strain from rising living costs. Asked about the plight of a 77-year-old woman who could not afford to feed herself and who spent her days travelling on buses to keep warm, the prime minister’s response was to claim credit – falsely – for introducing the subsidised transport regime that made her desolate journeys possible. It was a revealing moment not because it was insensitive or dishonest, although it was both. The telling feature was Johnson’s compulsion to relate the question back to the only issue in which he can sustain any interest – himself. Narcissism was less toxic when its bearer radiated good cheer. “Boris” the eternal optimist was a character who melted hard questions with a sunny disposition. But that persona has a twin, a sullen figure mostly hidden from the public eye but familiar to Downing Street insiders. This is brooding, needy Boris. He is always feeling betrayed and unappreciated. He is the kind of man who resents having his limelight blocked by a cold, hungry pensioner. Whichever Johnson is on display, his ego hogs all the political bandwidth available for the Conservative party. That poses a dilemma for MPs. They can have an agenda to address the country’s economic and social needs, or they can spend their energy deflecting and dissimulating to cover for their delinquent leader. They cannot easily do both. Actually, there is a third-way option. It involves pretending to be serious about government and hoping that something turns up. That method has served Johnson well enough in his career to date. A bet against him making a comeback is never safe. Local elections this week are forecast to go against the Tories, but not on the scale that would allow Johnson’s enemies to extrapolate certain general election carnage. A swing to Labour in line with current opinion polls would amount to a normal midterm punishment beating for an incumbent administration, not a seismic event. Keir Starmer has successfully stabilised his party’s position by neutralising the most voter-repellent properties of Corbynism, but Labour doesn’t exude the dynamic drive of a project poised for power. Effective opposition leaders have a way of galvanising general political malaise into impatience for regime change, and making themselves the obvious vehicle to achieve it. That energy is available to Starmer, but still untapped. He needs less of it with Johnson in Downing Street. Many Tories privately recognise that the Labour leader is morally and professionally more suitable for high office. That doesn’t stop them campaigning for their party, but it makes them less effective. As some Labour MPs found under Jeremy Corbyn, it is hard to be persuasive on the doorstep when you think your leader is unfit to be prime minister. Even the hardcore Johnson loyalists don’t look to him for leadership or principle. His merit in their eyes is the absence of both qualities. The right wing in particular likes the way he yields to pressure, like political memory foam, shaping the government’s plans to the ideological contours of the body that most recently sat on him. There is also a cadre of over-promoted mediocrities – the likes of Nadine Dorries and Jacob Rees-Mogg, too many to list them all – whose function in Johnson’s cabinet is to be grateful that the bar was set low enough for their admittance. That is a legacy of Brexit. It is the consequence of building an administration around an idea that made no sense as a plan for practical government. The price of joining Team Boris was giving up a place on Team Economic Reality, which diminished the pool of available talent. Johnson has undoubted political successes to his name, but they are campaign credits: two London mayoral elections; the Brexit referendum; the 2019 general election. The periods in between have been a mishmash of indolence, prevarication and scandal. He has bounced back before, but he has never previously had his morose, self-pitying persona exposed to as much scrutiny as its jovial, ebullient “Boris” alter ego. As prime minister, there is nowhere to hide. Tory MPs might also want to interrogate the sustainability of a political strategy built on one man’s unique ability to borrow votes from people who have never liked their party. Post-Johnson, London is Labour again. There are plausible grounds to think that the 2019 general electoral gains are more durable – that a profound cultural realignment occurred over Brexit in places where Labour support had decayed over many years. But if that were certain, Tories would be less fixated on the charismatic electoral voodoo that was their reason for making Johnson leader in the first place. Fear that no one could repeat the trick is their unvoiced reason for keeping him. That anxiety speaks volumes about the demoralisation and intellectual debilitation of many Conservative MPs. They have no respect for their leader, yet they are unable to imagine what they would be without him. Rafael Behr is a Guardian columnist