• The shock return of Brexit figurehead Nigel Farage to the political fray could be the final nail in the coffin for Prime Minister Rishi Sunak's ruling Conservative Party ahead of the upcoming U.K. elections.
• Tony Travers, professor at the London School of Economics, said the move marks a key step in Farage's aims of shifting the Conservative party further to the right — or eliminating it entirely.
• "The likelihood of them [the Conservatives] going below 100 seats is very real. Then that's a potential extinction event," Philip Blond, director of ResPublica, told CNBC.

LONDON — The shock return of Brexit figurehead Nigel Farage to the political fray could be the final nail in the coffin for Prime Minister Rishi Sunak's ruling Conservative Party ahead of its almost certain defeat in the upcoming U.K. elections.

Farage announced Monday that he would run in the U.K.'s July 4 election, less than two weeks after saying he would not stand as a parliamentary candidate to focus on supporting his friend and ally Donald Trump in the U.S. presidential race.

Euro-skeptic Farage said he will lead his right-wing Reform UK party — formerly known as the Brexit Party — and run for a seat in Clacton, a coastal town in the east of England, which saw huge support for the Leave campaign he orchestrated in the 2016 EU referendum.

The politician-turned-media personality's return adds momentum to the insurgent party. But, critically, it threatens to deprive key votes from the Conservatives, who are already trailing opposition Labour in the polls by a dramatic margin.

"Even if Reform don't win seats, they'll drain key votes away from the Conservatives," Olivia O'Sullivan, director of Chatham House's U.K. in the World programme, told CNBC over the phone.

The latest modeling, released moments after Farage's announcement, puts Labour on for an historic victory — greater even than Tony Blair's 1997 landslide — with the party gaining 220 seats to the Conservative's 225 losses. That would put Labour leader Keir Starmer on for a 422-seat majority in the 650-seat House of Commons.

Farage acknowledged Monday that Labour effectively had the election in the bag, but he said he felt he would be "betraying" voters if he did not offer them a viable right-wing option.

Tony Travers, professor at the London School of Economics, said the move marks a key step in Farage's aims of shifting the Conservative Party further to the right — or eliminating it entirely.

"The intention is to wound the Conservative Party so much that there is an opportunity for his Reform Party to replace them or a new version of the Conservatives to re-emerge with their views dominant in it," he told CNBC.

Tory 'extinction'

Farage has an ax to grind with the Tories. In the 2019 election, his then-Brexit Party agreed not to field candidates in hundreds of seats to safeguard a Conservative win. However, he has since accused the party of failing the political right, saying on Monday it was time for "revolt."

"What I'm really calling for — or what I intend to lead — is a political revolt," he told an "emergency" press conference in London.

The announcement marks a major blow to Sunak's earlier efforts to win right-wing votes by hardening the Tories' stance on migration and the U.K.'s membership of the European Convention on Human Rights. Recent announcements on the reintroduction of compulsory national service, tax guarantees for pensioners and new gender definitions were also seen as bid to woo would-be Reform voters.

"He's left with a nightmare problem," Travers said of Sunak. "It effectively concedes the Conservatives are not going to win marginal voters."

Indeed, Phillip Blond, director of independent, non-partisan public policy thinktank ResPublica, said the recent developments could mark "wipe-out territory" for the Tories, with the party potentially losing the seats necessary to remain a credible opposition party.

"It's pretty extreme," Blond told CNBC. "The likelihood of them [the Conservatives] going below 100 seats is very real. Then that's a potential extinction event."

A new Conservative leader

Electoral upheaval is just the latest in a series of scandals to hit the Conservative Party, which has undergone five prime ministers during its last 14 years in power.

As one of the world's longest running and most successful political parties, Travers said forecasts of electoral extinction were likely overblown. "History suggests the Conservative Party will find a way of recovering," he said.

However, questions remain over who may lead a Tory party re-emerged from the ashes.

Farage, for his part, has said "never say never" to the prospect of joining a "reset and realign[ed]" Conservatives. And according to Blond, the 60-year-old's ultimate leadership of a severely diminished Tory party is a "perfectly possible scenario."

"There may be one or two leadership figures, but one could imagine the Tories are so diminished in the popular mind that they think 'who can unify the right?' And the answer to that could only be Farage," Blond said.

Farage, while controversial, is seen as a deft political maneuverer, foreshadowing the rise of Western populist politics in the 2010s. A recent YouGov poll found him to be the U.K.'s most popular politician, outstripping Starmer in fourth place and Sunak in twentieth position.

Sunak and Starmer are set to face off later Tuesday in the first of a series of live TV debates ahead of next month's election.