Johnson would be PM with smallest personal majority since 1924
His constituency majority is only 5,034 and would be overturned on a swing of 5.4%.
Boris Johnson would have the smallest constituency majority of any new prime minister in nearly 100 years, were he to make it to Downing Street.
Mr Johnson has a majority of just 5,034 in his seat of Uxbridge & South Ruislip – the equivalent of 10.8% of all votes cast in his seat at the 2017 general election.
No prime minister since 1924 has assumed office with a smaller personal majority.
Mr MacDonald’s majority was the equivalent of 11.2% of all votes cast in his seat – slightly higher than the comparable figure for Mr Johnson in 2017.
When measuring majority in this way – as a proportion of all votes cast – Mr Johnson’s figure of 10.8% is the lowest since Andrew Bonar Law in 1922, whose personal majority was 8.0% when he became PM.
The largest personal majority of any incoming prime minister of the last 100 years is that of Theresa May.
She enjoyed a majority in her seat of Maidenhead of 29,059 – 54.0% – when she moved into 10 Downing Street in 2016.
Michael Gove, MP for Surrey Heath, has the largest (24,943).
Mr Johnson’s majority in Uxbridge & South Ruislip would be overturned by Labour on a swing of 5.4%.
By contrast, a swing of 21.6% would be needed to unseat Michael Gove.