LONDON — Labor Party politician Sadiq Khan, the son of a bus driver from Pakistan, led London’s mayoral race Friday, opening a lead over Conservative rival Zac Goldsmith that left him poised to be the city’s first Muslim mayor. Goldsmith, a wealthy environmentalist, described Khan as “dangerous” and accused his opponent of giving “platforms, oxygen and even cover” to Islamic extremists — a charge repeated by Prime Minister David Cameron and other senior Conservatives. Khan, who calls himself “the British Muslim who will take the fight to the extremists,” accused Goldsmith of trying to scare and divide voters in a proudly multicultural city of 8.6 million people — more than 1 million of them Muslims. The Conservatives under popular Scottish leader Ruth Davidson became the main opposition in Scotland’s Edinburgh-based parliament — an unprecedented situation in a region that had shunned the party for decades after the governments of Prime Minister Margaret Thatcher, whose policies cost thousands of jobs in mining and heavy industries. Thursday’s elections for local authorities and regional assemblies demonstrated the complexity of British politics in the final weeks before Britons vote on June 23 on whether the country should remain in the European Union.