British Prime Minister Rishi Sunak may be on course for a bruising defeat with his Labour Party rival Keir Starmer set for a landslide win, according to the definitive election night exit poll released on Thursday as polling stations across the country closed in the landmark UK general election.

According to the exit poll, which is often quite close to the final tally, Labour could win as many as 410 seats, comfortably crossing the halfway 326 mark and notching up a 170-seat majority with the incumbent Tories down to just 131 seats.

Sunak's future as leader of the Conservative Party now hangs in the balance, hours after the British Indian leader and the man who wants his job -- Starmer -- were among the first few voters to cast their votes along with millions in England, Scotland, Wales and Northern Ireland.

Sunak and his wife Akshata Murty walked hand-in-hand to their local polling booth on a sunny day in his constituency of Richmond and Northallerton in Yorkshire, northern England. A little later, Starmer, 61, and wife Victoria were at their polling station in Camden, north London, sporting Labour red colours.

Sunak, 44, was facing the impossible challenge of overcoming voter anger against the incumbent Tories after 14 years in power. The Keir Starmer-led Labour Party, meanwhile, maintained a strong lead over the Tories throughout the six-week campaign.

Both leaders wrapped up their poll pitches with contrasting messages -- Sunak urging voters not to hand "tax-raising" Labour a "supermajority" and Starmer playing down the prospect of a landslide win for fear of a low turnout impacting the final outcome.

Sunak continued to drive home the message on his X account, asking voters: "Can you trust Labour with a supermajority?" Candidates were fielded for 650 constituencies across England, Scotland, Wales, and Northern Ireland, with 326 required for a majority in the first past the post system. Besides the two main parties, voters were choosing from a list of candidates representing the Liberal Democrats, Green Party, Scottish National Party (SNP), SDLP, Democratic Unionist Party (DUP), Sinn Fien, Plaid Cymru, Workers' Party, the anti-immigration Reform Party and several contesting as Independent.

Around 40,000 polling booths were operating across the country from 7 am local time for an estimated 46 million registered voters to mark a cross next to their chosen candidate on a paper ballot.

Now that the booths have officially closed at the designated 10 pm local time, counting commences up and down the country right away, with the first results expected just before midnight local time. Sunderland in the north-east of England and Newcastle traditionally compete with each other to be the first to declare.

Sunak and his team's strategy in the final hours was to canvas their traditional voters to narrow the gap of a widely expected defeat after clear Tory majorities in the last three general elections. The Opposition dubbed it as fear tactics to jolt Tory voters into action, with the hope of keeping the Labour majority under that won by former prime minister Tony Blair led Labour Party in 1997 of 179 seats.

The Labour Party, meanwhile, was keen to override this message of its win as a foregone conclusion to fight against any complacency within the ranks and among its own voter base.

Polling experts have forecast a low turnout, which stood at 67 per cent in the last general election in December 2019 when Johnson won 365 seats, giving him an 80-seat majority. Labour won 202 seats, the SNP 48, the Lib Dems 11, DUP eight, Sinn Fein seven, Plaid Cymru four, SDLP two, Alliance party one, and Greens one.

The UK has a five-year general election cycle and Sunak had until January 2025 to go to the polls but chose a surprise summer election when he named July 4 as the polling date in May.

It is the first time Sunak is seeking the voters' mandate, having been chosen Tory leader and Britain's first Indian heritage Prime Minister by the party membership following political turmoil in October 2022. It is also the first test at the ballot box for Keir Starmer, who took over from Jeremy Corbyn after Labour's defeat in 2019.

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