How tactical voting might affect the British election

If an election were held tomorrow, our prediction model is sure that the Tories would lose. But it may still be being too kind, since it does not explicitly consider the potential for a jump in tactical voting. When the Conservatives have suffered landslide defeats in the past—as they did in 1906, 1945 and 1997—these have been at the hands of co-ordinated anti-Tory coalitions. Another such coalition may be forming now.

That is because of a big rise in the number of centre-left crossover voters who are prepared to cast their ballots for more than one party (see chart). This increases the chances that people will opt for a party other than their first choice in order to defeat the Tory candidate in their constituency. In 2019 around 17% of all voters were considering both Labour and the Liberal Democrats, compared with only around 13% in 2015. In May 2023 it was almost 22%.