While Reform UK's share of poll support has dropped by 3.4 percent from almost 30 percent in December, it is still comfortably in first place in seats. The current Electoral Calculus prediction shows Reform winning 266 seats. This would place it 159 seats ahead of the Conservatives and 197 seats ahead of the Labour Party.
Last December, Reform's higher vote gave it a predicted 325 seats, but that was still one seat short of an absolute majority in the Commons. Reform is now 60 seats short of an absolute majority. However, the new forecast indicates it still has a 16 percent chance of winning an absolute majority of seats.
The chief reason for Reform's big lead is that as the front-running party in the polls, Reform benefits most from the first-past-the-post system. For every one percent of the vote, it can gain ten MPs. By comparison, for every one percent of poll support that the Conservatives achieve, they gets fewer than six seats. Even though Labour is slightly ahead of the Conservatives in poll support, it can claim fewer than three seats for every one percent of the vote.
A second reason why Reform is still well ahead is that the surge in support for the Green Party is preventing Labour from benefiting through holding on to seats in which Reform is the chief challenger. The Green Party is currently predicated to win 74 seats; 68 of its gains would come from Labour. In addition, the Greens have reduced Labour's vote in hundreds of constituencies in which Reform is the governing party's chief challenger. Thus, 222 of the 266 seats that Reform expects to capture come from Labour.
The current bad omen for Reform is that the Conservatives have begun to show signs of gaining more seats. Last December, the Tories were expected to take only 54 seats. Now they are forecast to almost double that total to 107 MPs, with less than a one-percent gain in poll support. If this result were repeated at the next general election, it would be even worse than its 2024 result, which was the worst Tory showing in its history.
The difference in support in the polls and support in the House of Commons underscores the importance of focusing on MRP analysis to answer the question: Who will govern Britain after the next general election? While the March average of poll results shows Labour in second place in terms of voter preferences, the MRP-based prediction shows it in fifth place behind Reform, the Conservatives, the Greens and Liberal Democrats. If the Scottish National Party were to do as well against Labour in the next Westminster election as it could do in the May election for the devolved Scottish Parliament, this could push Labour into sixth place at the next UK election.
As long as other parties rule out giving Reform the parliamentary support it needs to win a vote of confidence in the House of Commons, then Reform's election victory would be short-lived. For the opposition parties' 384 MPs is more than enough to prevent it from taking control of Downing Street. The upshot would be another general election in which five opposition parties divide a big majority of the popular vote. They would also be fighting the first-past-the-post system, which could once again make Reform UK the biggest party in the House of Commons if it came first in the popular vote.
Prof Richard Rose's new book, "The Disruption of the British Party System: A Guide to the Next General Election" will be published by Manchester University Press in early June.