On Thursday, British voters appear almost certain to embrace momentous political change, handing the ruling Conservatives what could be a defeat of historic proportions, and casting their lot with the center-left Labor Party.

The widely forecast result — a resounding Labor win — would end Prime Minister Rishi Sunak’s 20-month tenure, and usher in a new government led by Keir Starmer, the 61-year-old head of the Labor Party (spelled Labour by the British.)

What is at stake?

British parliamentary elections must be held at least once every five years. Whichever party, alone or in coalition, can marshal a majority in the House of Commons — currently consisting of 650 seats — forms the next government. Its leader becomes prime…