UK Prediction Market Puts 36% Chance on Starmer Ouster by End of May

Prediction markets now price a 36.5% probability that Keir Starmer will no longer be prime minister by May 31, 2026, a 30-percentage-point jump in 24 hours as a Cabinet-level rebellion threatens his hold on power. Polymarket has seen $1.24 million in total volume on the contract, with $280,000 traded in the past day alone.

The crisis was triggered by Labour’s loss of nearly 1,500 council seats in local elections across England last week, with most seats going to Nigel Farage’s Reform UK. Four junior ministers resigned Monday evening, and more than 90 of Labour’s 403 MPs have publicly called for Starmer to resign or set a timetable for his departure, according to the BBC. That is not far short of the 81 signatures needed under Labour rules to trigger a formal leadership challenge.

Among the leading potential successors are Health Secretary Wes Streeting, former Deputy Prime Minister Angela Rayner, and Greater Manchester Mayor Andy Burnham. Streeting is scheduled to meet Starmer on Wednesday morning to discuss the way forward, though an ally said he would not make a statement after the meeting that might distract from the monarch’s speech. Burnham’s path to parliament remains uncertain: he was blocked from standing for a seat in January by Labour’s ruling body, though Downing Street now indicates it will not oppose his candidacy. One Labour MP has said he will step down to trigger a by-election, but Reform UK and the Green Party could still prevail in that contest.

Cabinet support for Starmer is eroding. Home Secretary Shabana Mahmood and Energy Secretary Ed Miliband have both privately urged the prime minister to consider a departure timetable, according to reports from Politico and Proactive Investors. At a Cabinet meeting Tuesday, Starmer refused to allow discussion of his own leadership and rejected a request from Streeting for a private meeting afterward. The cost of UK government borrowing surged on Tuesday as political uncertainty mounted.

The market’s move reflects the accelerating timeline. The probability of Starmer leaving by the end of this week was priced at 32% in earlier trade, rising to 57% by the end of May and 87% by the end of the year, according to Proactive Investors. While Starmer has told his cabinet he will “get on with governing” and warned that a contest would cause chaos, more than 150 MPs have indicated support for him or say now is not the right time for a challenge.

What to watch next: The 81-signature threshold for a leadership challenge. Streeting’s meeting with Starmer on Wednesday could prompt a formal declaration. If no candidate emerges soon, the pause may last months, as Labour factions remain divided and no single challenger has yet mustered enough allies to force a contest.