In the fallout from the further release of documents related to U.S. billionaire sex offender Jeffrey Epstein, Morgan McSweeney (49), chief of staff and closest aide to UK Prime Minister Keir Starmer, has resigned. The decision to cast aside the ‘kingmaker’ who made Starmer prime minister is being read as a painful act of self-sacrifice, but assessments suggest it is unlikely to contain the crisis amid intense calls for the prime minister to take responsibility.

The BBC reported on the 8th (local time) that McSweeney said in a statement that day, “The decision to appoint Peter Mandelson was wrong. I take full responsibility for having advised the prime minister on the appointment,” and stepped down as chief of staff.

Peter Mandelson, a senior Labour politician and former industry secretary, is under police investigation after allegations emerged in Epstein files additionally released by the U.S. Department of Justice that he received large sums from Epstein and leaked internal government information, among other misconduct. Prime Minister Starmer has faced criticism for appointing Mandelson as ambassador to the United States even when his ties to Epstein were publicly known, and McSweeney was reportedly the one who recommended the appointment.

In a statement issued after McSweeney announced his resignation, Starmer said, “Thanks to his dedication and leadership, we were able to win a landslide,” adding, “Our party and I owe him, and we thank him.” Vidya Alakeson and Jill Cuthbertson were appointed as acting cochiefs of staff, but concerns are being raised that they may not carry the same political weight as McSweeney.

The Times assessed the decision by saying, “To calm backlash within Labour and keep his premiership, Prime Minister Starmer sacrificed a ‘closest political ally.’” Only a few days ago, Starmer had publicly praised McSweeney as “the core of the team,” but ultimately accepted his resignation. Senior Labour figures said Starmer made the call out of concern that hundreds of thousands of emails and social media messages exchanged between Mandelson and McSweeney could be released. If disclosed, they judged, it could reveal the influence Mandelson has long exercised over the prime minister’s closest aide.

The Guardian analyzed that “McSweeney’s resignation is highly symbolic, as it marks the exit of the figure who played a decisive role in Starmer’s ascent to Labour leader and prime minister.”

After Labour’s crushing defeat in the 2019 general election, McSweeney devised a strategy to install a centrist candidate whom the left would find hard to reject as party leader and then gradually shift the party to the center. The person he picked was Starmer, a human rights lawyer and former head of the Royal Police Agency. McSweeney ran Starmer’s leadership campaign, and Starmer was elected Labour leader with 56% of the vote. He also played a decisive role in Starmer’s rise to prime minister by leading the 2024 general election strategy.

McSweeney’s influence over Starmer was absolute. According to the recently published book <Get In>, one Labour figure said, “Keir isn’t the one driving the train. He thinks he’s driving, but in fact he’s just sitting in the front seat of a driverless train.” In other words, the real ‘driver’ was McSweeney. This adds weight to the view that the shock of losing the ‘kingmaker’ will be considerable.

Labour’s leadership is seeking to rally the party. Pat McFadden, secretary of state for work and pensions, warned against division, saying a leadership shake-up is not the answer, and former home secretary David Blunkett also called for restraint. However, left-wing MPs say McSweeney’s resignation alone is not enough and continue to press the case for Starmer’s responsibility.

The opposition’s offensive is also intensifying. Kemi Badenoch, leader of the Conservative Party, criticized Prime Minister Starmer, saying, “Blaming others again,” and, “Starmer just says ‘Mandelson misled me’ or ‘McSweeney advised me,’ but he doesn’t take responsibility for his terrible decisions.”