What is at stake in the Chesham and Amersham by-election on Thursday?

After a long period of drought, we are now halfway through a series of four parliamentary by-elections in quick succession. There had been no by-election since Brecon and Radnorshire in August 2019, won by Jane Dodds for the Liberal Democrats (who then lost in the general election four months later), until the Hartlepool contest last month.

Labour’s defeat in Hartlepool was significant, crystallising the view that, although Keir Starmer had started well as leader of the opposition, he is struggling to make his mark against a vaccine-boosted prime minister.

A second by-election a week later, by contrast, was barely noticed, as Anum Qaisar-Javed retained Airdrie and Shotts for the Scottish National Party after Neil Gray gave up the House of Commons for a seat in the Scottish parliament.

The next by-election, this Thursday, is different again. It is the first by-election caused by the death of a Conservative MP since Eric Forth died in 2006. In this case the vacancy was created by the death from cancer of Cheryl Gillan, a former cabinet minister – she was Welsh secretary in David Cameron’s first government.

Usually, the Liberal Democrats would see a by-election in a seat such as this as an opportunity. It’s a home counties constituency some distance from the Greater London boundary but notable for being on the London Underground network. The Lib Dems came a fairly distant second at the general election, but with a Labour and Green vote that could be squeezed, the 15-point swing needed to win the seat is the kind of thing the Lib Dem by-election machine has achieved many times before. Given the Brexit dimension of politics that was so evident in Hartlepool, it is also significant that the constituency voted by 55 per cent to remain in the EU in the referendum.

The Lib Dems have a strong candidate, Sarah Green, although she possibly should not have described her party as “the cockroaches of British politics”. She meant to say that they are hard to eradicate and keep coming back, but the conditions are poor for a traditional Lib Dem protest-vote by-election win. For one thing, the Lib Dems’ national profile has been so low since the general election that the Greens are now threatening to overtake them in the polling averages. Some commentators have looked across to the success of the Greens in Germany to speculate that they could replace the Lib Dems as the natural repository of third-party protest votes here. (Others have even suggested that the Lib Dems and Greens should merge.)

The Labour Party is not fighting this by-election vigorously, although its candidate, Natasa Pantelic, who is a parliamentary assistant to Chris Bryant, the Labour MP, gained a video endorsement from Tony Blair. Labour sources suggest an unspoken deal with the Lib Dems, in return for a low-key Lib Dem campaign in the forthcoming Batley and Spen by-election, which Labour is fighting hard to hold.

Nevertheless, the state of national politics does not seem favourable to an anti-government protest vote. Public opinion remains broadly supportive of the Conservatives and the prime minister for their handling of the vaccines. Peter Fleet, the Tory candidate who is chair of the Retail Automotive Alliance, is the heavily odds-on favourite to win on Thursday.

Then all eyes will turn to the fourth by-election in the current sequence, where Labour is desperate to avoid losing Batley and Spen on 1 July. If there were a credible alternative to Starmer as Labour leader, defeat in another Labour Leave northern seat would mean that his position would be under threat; as it is, defeat will simply be seriously demoralising.