The Manchester Arena bombing was not only the deadliest terrorist attack in Britain since the London bombings in July 2005 but the first mass killing to take place during a general election campaign.
It came at a crucial moment in the campaign, with Theresa May under pressure after a major policy U-turn, while Labour's poll numbers are rising.
The prime minister and Labour leader Jeremy Corbyn spoke by phone at 4am on Tuesday morning, and agreed to suspend political campaigning until further notice. The campaign will remain suspended at least until Thursday and possibly until the weekend but the bomb attack is certain to have an impact on both the tone and the content of the campaign.
The moratorium itself will halt the momentum that has seen Labour recover in the polls throughout Britain and reclaiming the lead from the Conservatives in Wales. It will also distract voters’ attention from the chaos that entered the Conservative campaign last weekend, as the party panicked in the face of hostility towards its proposal to make the elderly pay for their own home care.
May, who had placed her “strong and stable” leadership at the centre of the Conservative campaign, made an ungainly U-turn, dramatically altering a key policy just four days after it appeared in her party’s manifesto.
National security
To make matters worse, she then repeatedly denied that anything had changed, making her appear slippery as well as flaky.
The terrorist attack in Manchester has forced the prime minister back onto the territory where she is most experienced, dealing with national security. As a former home secretary, she is intimately familiar with how Britain’s security, policing and intelligence systems work, what they are capable of and what is impossible.
It has also demanded that she put aside the role of campaigning politician and return full-time to that of prime minister, making statements in Downing Street, visiting emergency services in Manchester and offering reassurance to the public. Later this week, she will play that role on a global platform when she attends meetings of Nato and G7 leaders.
For Corbyn, the Manchester attack follows a sustained Conservative campaign to portray him as soft on terrorism because of his past support for Sinn Féin and the Troops Out movement. He must fear that in the anxious atmosphere following the bombing, voters may conclude that he is a risk they cannot afford to take.