Who Are the Key Players in the UK Election?

Thursday’s general election is a pivotal moment for Britain after 14 years of Conservative Party government. Polls suggest that the center-left Labour Party is set to return to power in what would be a fundamental realignment of British politics.

Millions of voters in 650 constituencies are voting for candidates to represent them as members of Parliament. The political party that wins the most seats usually forms Britain’s next government, and that party’s leader also becomes prime minister.

To win an overall majority, a party must secure 326 seats. If the top party falls short of that, it can try to form a government with backing from other parties.

Here’s a look at the key parties and players in the race:

Conservative Party

Leader: Prime Minister Rishi Sunak

Mr. Sunak took office in October 2022, succeeding Liz Truss, whose sweeping tax cut plan spooked the financial markets and forced her out of office after just seven weeks. But Britain’s high mortgage rates and stagnant economy have persisted, and under Mr. Sunak, the Conservatives have suffered stinging losses in parliamentary special elections and elections for mayors and local councils.

Defenders of Mr. Sunak, 44, say he is a victim of the global economic headwinds coming out of the coronavirus pandemic, and argue that he deserves credit for steadying the markets. But critics say he never followed that up with a convincing strategy to recharge growth. Nor did he fulfill two other promises: to cut waiting times in the National Health Service and to stop the small boats carrying asylum seekers across the English Channel. Some say that Mr. Sunak, a onetime Goldman Sachs banker whose wife is the daughter of an Indian technology billionaire, is simply not relatable.

Labour Party

Leader: Keir Starmer

Labour has maintained a double-digit lead in the polls for more than 18 months. Mr. Starmer, 61, a former public prosecutor and human rights lawyer, has methodically repositioned the party as a center-left alternative to the divided, erratic, sometimes extremist Conservatives. If Labour prevails, Mr. Starmer would become the party’s first prime minister since Gordon Brown left office in 2010.

A Labour government would operate under strict financial constraints, which has raised questions about whether Mr. Starmer would have to raise taxes to pay for promised investments in the N.H.S. and other public services. While he has issued a blanket promise not to raise taxes on “working people,” Labour is expected to raise taxes on oil and gas companies, private equity firms and high-income foreigners who live in Britain.

Leader: Nigel Farage

A small anti-immigration party, Reform has risen in the polls in recent months, and Conservative officials fear it could siphon away supporters from their candidates. Mr. Farage, a champion of Brexit and a vocal supporter of Donald J. Trump, originally said he would not run in the election, but changed course last month when he announced he would stand for Parliament in Clacton, a small seaside town where 70 percent of voters chose Brexit in 2016. That has shaken up the race and could help Labour by dividing the right-wing vote.

Liberal Democrats

Leader: Ed Davey

The Liberal Democrats, a small centrist party, are well placed to win seats in affluent areas like Surrey, where right-leaning voters find the party more palatable than Labour. The Lib Dems made health and social care major priorities of their campaign, and were helped by Mr. Davey, 58, who spoke movingly about his personal struggles, including caring for his disabled teenage son. He also subjected himself to publicity stunts, including bungee jumping and paddle boarding, trying to draw attention away from the party’s bigger rivals.

Other parties

In Scotland, the once-dominant Scottish National Party has been weakened by a funding scandal and the departure of Nicola Sturgeon as first minister, giving Labour a chance of picking up more seats there and easing Mr. Starmer’s path to becoming prime minister. The Green Party made sizable gains in local elections in early May, and pre-election polling suggested that it was picking up support among left-wing voters, especially 18- to 24-year-olds, alienated by Labour’s move to the center.