LONDON — Britain’s governing Labour Party has been plunged into a deputy leadership contest following the resignation of Keir Starmer’s scandal-hit second-in-command Angela Rayner.

The contest comes at a terrible time for a prime minister who hoped to turn around his fortunes in back-to-school week with a low-key refresh. Instead Starmer has given his detractors even more cause to grumble after he was forced into a full-blown weekend reshuffle in which the Home Office and other departments were completely overhauled, and newbie MPs with strong links to No. 10 were promoted.

Throwing a deputy leadership contest into the mix is unlikely to calm the nerves of an already fractious parliamentary party staring down the barrel of a massive poll lead for Nigel Farage’s Reform UK. Here’s what you need to know — and who’s likely to be in the running.

First, the process

A full meeting of Labour’s ruling National Executive Committee (NEC) is due to kick off at noon Monday for members to agree a timetable and code of conduct for a deputy leadership contest.

Plans are in the works for a hustings with MPs Wednesday, before MP nominations close at 5 p.m. Thursday. This draft timetable (which the NEC will be asked to formally adopt Monday, and could reject) would then need candidates to seek local party and union/affiliate nominations between Sept. 13-27 followed by a ballot of members from Oct. 8-23.

Given they need 80 MP nominations each, this would mean deputy leader hopefuls need to move fast.

According to the rulebook MPs must get the support of 20 percent of the Parliamentary Labour Party to stand plus the support of three affiliates (of which two must be affiliated trade unions) or 5 percent of Constituency Labour Parties (CLPs). It’s a high bar. Anyone who makes it through will then have to charm the members and affiliated supporters who will then vote in a preferential ballot.

Already the Labour left isn’t happy with the proposed timetable. Richard Burgon described it as the “mother of all stitch-ups” last night after hearing there would be just a couple of days for candidates to secure MP nominations. John McDonnell said it was “pretty clear leadership wants to bounce their own candidate thru.”

Many of the Labour figures POLITICO’s London Playbook spoke to Sunday night see the contest shaping up as a battle between a favored candidate for No. 10, voted for by the government payroll, versus someone backed by the backbenchers (and potentially the unions too). Here are our runners and riders list after MPs spent a frantic weekend trading intel and taking soundings.

Shabana Mahmood

Mahmood’s recent promotion to home secretary demonstrates her strong standing with Keir Starmer and would make her an obvious candidate favored by No. 10. But her Blue Labour-style politics will put off those party members who still tilt left, while her burgeoning Home Office in-tray means she has a lot on her plate.

David Lammy

After taking the deputy prime minister mantle from Angela Rayner (a consolation for losing those cushy government flights) there could be a case for Lammy going for her old deputy leader gig too. But huge pressure from MPs and unions for a female deputy means the new justice secretary’s gender could work against him.

Alison McGovern

There has been weekend chatter about McGovern, shuffled from the DWP to housing, and could be more given she is due at a long-arranged fringe panel at the TUC Congress this lunchtime. One union ally reckons McGovern (a former Progress chair who was also a big fan of Gordon Brown) has the potential to be a compromise candidate for No. 10 backing: “She’s a minister but she doesn’t have the toxic baggage.”

Rosena Allin-Khan

The A&E doctor came second in the last deputy leadership contest and is being urged to stand again. While unlikely to go all-in on attacking the leadership, her rebellion on Labour’s welfare reforms and criticism of the government’s Gaza policies could endear her to parts of the membership.

Emily Thornberry

She confirmed Sunday she is “thinking about” standing for deputy leader. The Foreign Affairs Committee chair — who was passed over for a Cabinet job by Starmer — has been increasingly critical of the prime minister, and warned further mistakes could lead to “hand[ing] our country to Farage.” (St. George flags and all.)

Louise Haigh

Her name was being floated over the weekend, nine months after she was effectively forced to resign from Starmer’s Cabinet over a decade-old fraud conviction. A standard-bearer of the soft left, an ally of the unions like Rayner and could be a headache for No. 10 (though an ally told PoliticsHome’s Sienna Rodgers she isn’t planning to run).

Lisa Nandy

Another soft-left politician being urged to run by some MPs, though Playbook heard from a couple of people last night that she was privately downplaying the chances of a run. The culture secretary has plenty on her plate given she kept her Cabinet job — despite months of on-off briefing that she could face the sack.

Sarah Owen

The Women and Equalities Committee chair has strong union links as a former GMB political officer and is described by union officials as a good organizer. Like many of her colleagues, she signed the rebel reasoned amendment that ultimately scuppered the government’s planned welfare cuts. Not much of a public name (yet).

Anneliese Dodds

As a former party chair Dodds knows Starmer’s party anatomically, and she has kept her powder dry since resigning over aid cuts in February — so polite she even held back the letter until after the PM met Donald Trump. The ex-development minister’s name was being raised over the weekend though some MPs may want someone more brash.

Lucy Powell

She was sacked as Commons leader in last week’s reshuffle after years in the Starmer project, including helping lead the review of the 2019 election defeat published by Labour Together (along with Mahmood). Her name was floated along with Haigh’s over the weekend by Greater Manchester Mayor Andy Burnham.

Dawn Butler

The long-serving left-winger was the first eliminated in the 2020 contest but is reported to be considering another run (although she also previously said she’ll put her hat in the ring for London mayor when Sadiq Khan steps down). She has already called for members to get a “meaningful say.” Hint, hint.

Miatta Fahnbulleh

The newly-reshuffled MHCLG minister’s name has mentioned a little over the weekend but it would be surprising for a new MP to become deputy leader — even one with a long Labour-friendly history at the IPPR and the New Economics Foundation.

And many, many more

This massive range is extraordinary, given the MP nomination threshold suggests there will be no more than about three candidates by the end of the week. Other names that’ve been thrown about include campaigning backbencher Stella Creasy and Liaison Committee Chair Meg Hillier … high-profile Cabinet ministers, including non-reshuffled Net Zero Secretary Ed Miliband and Education Secretary Bridget Phillipson, and Starmer uber-loyalists Steve Reed and Peter Kyle.

This list originally appeared in POLITICO London Playbook.