Stockton South, which Boris Johnson visited on Thursday, is one of the Conservatives’ top targets to take from Labour.
It ranks at number 12 on a list of Labour seats most vulnerable to the Tories, and would change hands on a swing of 0.9%.
Paul Williams won the seat from the Conservatives at the 2017 election, but only just – his majority was 888 votes.
Stockton South will be a two-horse race between Labour and the Conservatives, who won 49% and 47% of the vote respectively in 2017.
It is the type of seat the Tories need to take if they hope to form a majority government.
The party held the constituency from 2010 to 2017 – one of a very small number of Conservative seats in the North East – and they will be desperate to win it back.
Labour held Stockton South from 1997 to 2010.
It is a seat where Brexit could play a key role in determining which party emerges victorious.
The local authority area that includes the constituency is Stockton-on-Tees, which voted 61.7% Leave in the 2016 EU referendum.
Other Labour seats the Tories are targeting in north-east England include Bishop Auckland (which would fall on a 0.6% swing), Darlington (3.7%) and Tony Blair’s former constituency of Sedgefield (7.3%).