Maja Smiejkowska/Reuters
British Prime Minister Rishi Sunak delivers the soggy speech outside London's 10 Downing Street, on May 22.
London CNN  — 

UK Prime Minister Rishi Sunak announced a snap general election for July 4 in a statement outside Downing Street on Wednesday evening, as his Conservative Party faces an uphill struggle to extend its 14 years in power.

Sunak said outside Downing Street that he had informed King Charles III of the rare summer poll, firing the starting gun on a six-week campaign that is almost universally expected to conclude in the demise of his Conservative government.

Soaked by a downpour as he spoke, Sunak said: “Now is the moment for Britain to choose its future.” He also attacked his opponents, saying that by voting for the Labour Party, Britain would “risk going back to square one.” But he admitted: “I cannot and will not claim that we have got everything right.”

Sunak was required to hold a vote by January 2025, and had long resisted calls to be specific about his plans. But a fall in inflation rates, announced earlier Wednesday, provided the backdrop for his announcement.

The move will be welcomed by the buoyant Labour Party, led by Keir Starmer, which is soaring in the opinion polls and has sought to present itself as a reformed and moderate group that is ready for power.

In the wake of the announcement, Buckingham Palace said the British royal family would postpone engagements “which may appear to divert attention or distract from the election campaign.” The King and Queen’s D-Day memorial engagements in June are expected to go ahead as scheduled.

In his speech, Sunak sought to paint external factors such as Covid-19 and the war in Ukraine as the context to Britain’s economic struggles, saying the two factors combined represented “the most challenging times since the Second World War.”

But he battled heavy rain that soaked his suit in just minutes, and he was almost drowned out by a loudspeaker outside the Downing Street gates, through which a protester blared D:Ream’s “Things Can Only Get Better,” the theme song of Labour’s big election win in 1997.

Starmer was quick to respond to Sunak’s announcement. Speaking at an indoor news conference, the opposition leader said: “Tonight the prime minister has finally announced the next general election.”

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He framed the vote as a “chance to change for the better – your future, your community, your country.”

“It will feel like a long campaign, I’m sure of that, but no matter what else is said and done, that opportunity for change is what this election is about,” he said.

Current polling is dire for Sunak; Labour begins the campaign around 20 points up on average, with the Tories often closer to third-party challengers such as Reform and the Liberal Democrats than they are to Labour.

When converted to a projection of seats in parliament, those figures indicate either a comfortable Labour win or a potential electoral wipeout for the Conservatives.

Sunak will hope that a shrewd campaign could result in a spectacular upset for Labour and extend a period of Tory rule which began in 2010 and has overseen austerity economics, Brexit, the Covid pandemic and a cost of living crisis.

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Sunak walks back inside on Wednesday after announcing the July 4 date for the election.

He is the fifth Tory leader to serve during that time, taking over from the ill-fated Liz Truss, whose disastrous term imploded just six weeks after it began and exacerbated the financial woes crippling the United Kingdom.

Sunak’s party will likely put his efforts to tackle illegal migration at the center of his campaign; a recent move to deport some asylum seekers to Rwanda finally became law last month, and the first flights could potentially leave during the campaign.

But Labour will seek to highlight the government’s struggles to ease soaring prices, the state of Britain’s over-stretched healthcare service, and the sleaze scandals that have tanked the Tories’ reputation among a large swath of British voters.

Smaller parties could upend the designs of the two dominant groups, even if it is virtually impossible for them to return a government. The new, anti-migration Reform Party and the centrist Liberal Democrats will look to challenge Sunak in some of his party’s historical strongholds, complicating his efforts to hold power.

North of the border, the pro-independence Scottish National Party will hope to hold off a Labour challenge and regain its dominance in Scotland’s politics despite a rocky period and the recent ascension of its third leader in 15 months.

The Conservatives under former Prime Minister Boris Johnson won a healthy majority in the last UK-wide vote, in December 2019, pledging to push through Britain’s exit from the European Union – an issue that had transfixed politics in the country for more than three years.

But Johnson’s premiership collapsed after a string of scandals, paving the way for his then-finance minister Sunak to emerge as a frontrunner for the leadership.

Adding to the sense that the Conservatives are nearing the end of their time in power, dozens of Tory MPs — including former cabinet ministers and ex-Prime Minister Theresa May — announced they would not seek re-election.

But recent election and referendum campaigns have proved volatile, and Tories still publicly hopeful of success have pointed to mixed levels of enthusiasm for Labour’s offering.

The vote will take place on Thursday July 4 in all of the UK’s 650 parliamentary constituencies, and counting will occur overnight, with the two main parties seeking to cross the 326 mark needed for a majority.

A government will be formed as soon as that mark is crossed, and take charge immediately, pending the symbolic approval of King Charles III.

This story has been updated.

CNN’s Luke McGee and Sophie Tanno contributed reporting