A test for Burnham's premiership

The byelection is being read as a measure of the political landscape under Andy Burnham, almost three months into his premiership. Burnham succeeded Starmer as prime minister in July, and the contest is his first significant electoral test since taking office.

The result may indicate whether Burnham's recovery in national support is translating into Labour's inner-city strongholds, and whether the Greens keep attracting younger and progressive voters. It came as Burnham pitched a more ambitious offer to progressives at his first Labour conference as prime minister.

The Greens' challenge under Zack Polanski

Zack Polanski has run an energetic campaign, mobilising thousands of activists and leaving the Green party conference early after his speech to campaign in the constituency, in an attempt to prove he and the Greens are a serious rival. The party hopes to repeat its byelection victory in Gorton and Denton in February, where it overturned a Labour majority.

Polling has shifted in the months since that Greater Manchester win, when YouGov put the Greens on 21%, a few points ahead of Labour. The latest YouGov survey put the Greens 16 points behind Labour, which was on 27%.

In an interview with the Guardian last Friday, Polanski called the contest "probably 50/50" and said it was "really on a knife-edge". Asked whether losing would undermine his position, he said: "It doesn't depend on it whatsoever."

He has argued that electing him would push Labour towards stronger rent controls, greater action on the climate crisis and public ownership of Thames Water. Senior Green figures privately fear defeat could badly damage his reputation, amid concerns that the party's increase in members has not translated into an advantage in campaigning. He has also faced questions about his authority, having been accused of being unable to articulate his thoughts on motions that became policies at his party's conference.

Labour's candidate Sagal Abdi-Wali

Labour's candidate is Sagal Abdi-Wali, the 42-year-old leader of Camden council, who arrived in Britain as a child refugee after her family fled civil war in Somalia. She has presented herself as locally rooted, with experience of community work, homelessness and housing policy.

The seat and the shadow over the final days

Holborn and St Pancras is a young, diverse constituency:

• •Almost half of residents are aged between 18 and 34
• •About 45% of residents were born overseas

Those demographics matter because younger leftwing voters became disillusioned with Labour under Starmer's leadership over issues such as housing, the climate crisis and the war in Gaza.

The campaign's final days were overshadowed by Green party members voting to adopt a policy equating Zionism with racism, which passed by 1,022 votes to 813. Four of the party's five MPs opposed the motion, and Polanski, who is Jewish, left the conference early and did not vote.

The result is expected to be announced between 2:30am and 4am on Friday.