The announcement of July 4 for the UK general election took many by surprise. A key question is why it was called then when it did not have to be? The decision to call an election is always a gamble – there is perhaps no right time – and many factors feed into that call.

Legally, a general election had to be called in 2024. Behind the scenes, those in Number 10 will have been modelling when the vote should be held with the help of key economic indicators such as inflation and gross domestic product (GDP), as well as analysing the polls and speaking to focus groups.

In the UK, the power to request a dissolution of parliament and call an election lies with the prime minister. The party in power uses a process known as “evidence-based diagnostics”, in which evidence is collected regarding the state of the UK and analysed alongside voter perceptions, in an attempt to identify the best time – for them – to call an election.

This is complex, as it includes an assessment of the strengths and weaknesses of rival parties, and of independent analyses published by organisations such as the World Bank, the Organisation for Economic Co-operation and........

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