British Conservative politician Rishi Sunak late Friday reached the minimum threshold to run for party leader, as former prime minister Boris Johnson targeted an audacious comeback.

Cabinet member Penny Mordaunt became the first to formally declare her candidacy, after the UK’s ruling party was forced into a second leadership contest following the dramatic resignation of Prime Minister Liz Truss.

“Honoured to be the 100th Tory MP to support #Ready4Rishi,” senior backbencher Tobias Ellwood tweeted, as other backers of Sunak also said he had crossed the barrier.

Sunak will automatically become party leader and prime minister if his opponents fail also to win 100 nominations from their fellow Tory MPs.

Security minister Tom Tugendhat, who ran for leader himself after Johnson was toppled in July, issued a thinly veiled appeal to the scandal-tainted ex-leader to stay out of the race.

“This is no time for political games, for settling scores, or for looking backwards,” Tugendhat said as he also endorsed Sunak late Friday.

Neither Sunak nor Johnson has publicly declared they are running.

But Johnson cut short a Caribbean holiday to take part in the accelerated contest, which will see Tory MPs hold a vote on Monday before a possible online ballot for party members next week.

James Duddridge, one of Johnson’s closest allies in parliament, said he had been in contact with his old boss via WhatsApp.

“He said… ‘We are going to do this. I’m up for it’,” the MP said, as a Sky News reporter posted a photograph apparently showing Johnson on a flight home from the Dominican Republic.

The Sunak and Johnson camps are reportedly seeking talks to see if there is scope for a unity deal — although there is plenty of bad blood since the former prime minister’s defenestration.

With inputs from NDTV