Britons voted Thursday in local and regional elections that will choose a new mayor for London — and are expected to deal a blow to Britain's main opposition Labour Party.

Voters are electing a Scottish Parliament and legislatures in Wales and Northern Ireland, as well as choosing members of many English local authorities, including a new London mayor to replace flamboyant Conservative Boris Johnson.

The mayoral race pits the Labour Party's Sadiq Khan against Conservative Zac Goldsmith. Pollsters and bookies make Khan the favorite to win and become the city's first Muslim mayor, after a bitter campaign that saw Goldsmith accuse his rival of sharing platforms with Islamic extremists.

Khan, a former human rights lawyer and the son of a bus driver from Pakistan, accused wealthy environmentalist Goldsmith of trying to divide voters in one of the world's most multicultural cities, home to 8.6 million people — more than 1 million of them Muslims.