The Staggers 14 May 2021 Who will win the Chesham and Amersham by-election? The contest is well-placed for the Liberal Democrats, but don’t overlook the power of the Greens. Sign UpGet the New Statesman's Morning Call email. Sign-up The tragic death of Cheryl Gillan, the Conservative MP for Chesham and Amersham and former secretary of state for Wales, means there will be a by-election in her seat. Although the constituency comfortably returned Gillan in December 2019, it is probably the best opportunity for the Liberal Democrats to take a seat via a by-election in this parliament. The area voted heavily to remain in the European Union, and while Gillan was a committed Brexiteer, she worked the constituency hard and was well-liked. Chesham and Amersham is one of a small number of Conservative constituencies where the majority in 2019 was smaller than it was in 2010. The Liberal Democrats finished a clear second place in 2019 and over the past three decades they have generally been the most significant challenger to the Tories. They have the advantage of a relatively large Labour and Green vote to squeeze, and a good local message in their opposition to the Conservatives’ planning reforms. A gain is plausible: but a "good" result for the party would be a close-run thing, akin to the Witney or Bromley by-elections. [See also: What the SNP by-election win tells us about Labour’s predicament] There are two important buts at work however. The first is that the Conservatives, as the defending party, can set the date of the by-election and will, presumably, set it on 24 June, the first Thursday after the easing of lockdown restrictions, or some time around then. This should be highly favourable for them, despite the election being in a part of the south where they went backwards even in the highly favourable circumstances of both 2019 and 2021. The second, and probably much more important "but" is that it is also probably the best opportunity for the Green Party to have an impact at a by-election this parliament. The Greens did well in the local elections here. They finished below the Liberal Democrats, but gained ground on 2019. A win is a bridge too far, but there’s a very basic political incentive here: anything which means we talk about "the Liberal Democrats and Greens" is a good thing for the Greens, who have solid aspirations and a credible path to becoming England’s third party, and is bad for the Liberal Democrats, England’s perennial third party but one that faces serious political challenges. The Liberal Democrats need the conversation to be about "who is best-placed to defeat the Conservatives in close to 100 constituencies?" while the Greens are best-served if the conversation at the next election is "Liberal Democrats and Greens in a race for third". [See also: What Tony Blair gets right about Keir Starmer’s predicament] There’s a weird mix of incentives here: a Liberal Democrat-Green pact, of the kind that allowed the Liberal Democrats to win Richmond Park in the 2016 by-election and Brecon and Radnorshire in the 2019 by-election, may mean – unless it turns out the final end to lockdown has a significantly bigger increase in government support than the vaccine roll-out – that the Liberal Democrats could win the seat. A Conservative hold in which a strong Green performance is the difference between a Liberal Democrat win and a Tory one is something of a problem for the Green Party. But one in which the Liberal Democrats and Greens are closer to one another’s vote than the Conservatives is probably better news for the Green Party than facilitating another Liberal Democrat gain in the midterm. [See also: How blue has the Red Wall turned?] › How the debate over trans rights is splitting the SNP Stephen Bush is political editor of the New Statesman. His daily briefing, Morning Call, provides a quick and essential guide to domestic and global politics. He also co-hosts the New Statesman podcast. Subscribe For more great writing from our award-winning journalists subscribe for just £1 per month!