The polls have opened in local and mayoral elections in England, Wales and Scotland.
Several big-hitters from the labour movement, such as former cabinet minister Andy Burnham, are seeking power in the first raft of metro mayor votes.
Council elections are taking place at the same time with 4,851 seats up for grabs across 88 councils.
Every local authority is being voted on in Scotland and Wales while 34 councils are holding elections in England.
The full list of Labour candidates for the combined authority elections, known as metro mayors, is as follows:
Cambridgeshire and Peterborough – Kevin Price, a councillor and longstanding Unite member, faces a tough challenge in what is seen as a Tory stronghold.
Liverpool – Steve Rotheram, MP for Liverpool Walton who served as an aide to Jeremy Corbyn, looks certain to be elected.
Greater Manchester – the former health secretary and ex-leadership contender Andy Burnham is the overwhelming favourite.
West of England – Lesley Mansell, a Corbyn-backing councillor and NHS equality and diversity manager, faces a tough fight to take the semi-rural patch.
West Midlands – Sion Simon, the outgoing MEP and former MP, faces a tough fight against Andy Street, the former John Lewis boss, who is running for the Tories.
Tees Valley – Sue Jeffrey, the leader of Redcar and Cleveland council, is tipped to win and has put the fight for jobs at the heart of her campaign.