Voters will cast their ballots in the Birmingham Erdington by-election triggered by the death of popular Labour frontbencher Jack Dromey.
The polls in the seat held by Mr Dromey at the last general election with a majority of 3,601 votes over the Conservatives open at 7am on Thursday.
Paulette Hamilton is contesting the seat for Labour, while fellow city councillor Robert Alden is vying to become the first Tory MP there since 1936.
Anything but a Labour victory would be seen as a major upset for the party. The Conservatives have come close in the past when they lost by just 231 votes in 1983, when leader Margaret Thatcher was at the peak of her powers after the Falklands War.
Boris Johnson’s party has been struggling in the national polls as the Prime Minister was battered by allegations of parties in Downing Street breaching coronavirus rules.
The family of Mr Dromey, a shadow minister married to Labour grandee Harriet Harman, said he died suddenly at the age of 73 in his flat in the constituency in January.
The former leading trade unionist had represented Birmingham Erdington since 2010.