In a system of multi-party competition, if the Labour government's seats go down below what's needed for a parliamentary majority, it does not follow that the Conservative share goes up to the magic number of 326 seats in a 650-seat House of Commons. Even though Labour's loss of support in the polls could leave it with only 311 seats in the next House of Commons, it would still be 104 seats ahead of the Conservatives.
Even if Labour lost its arithmetic majority in the House of Commons it could have the political majority needed to keep control of government for a decade. Since Sinn Fein traditionally abstains, at most no more than 643 MPs are likely to participate in a vote of confidence. The 11 Independent MPs returned as Labour or leftwing candidates are more likely to abstain than vote to bring down a Labour government and risk installing a Tory government in its place. If these abstentions happened, there is a 24 percent probability that Labour would win the 316 votes needed to have a majority in a vote of confidence.
Even if Labour's support fell below 300 seats it could still keep the keys to 10 Downing Street by forming a coalition government with the Liberal Democrats. Their support in the opinion polls remains steady. Even a revival of Conservative fortunes would leave the Lib Dems with a better than 90 percent chance of winning more than half the 72 seats they took in July. If the Liberal Democrats were to hold all these seats, then Labour would need to win only 254 constituencies to head a coalition government with an absolute majority.
The Conservatives made made a net gain of 3 percent from where they were when wiped out at the July election. This would likely give it 86 more seats but still leave it with fewer MPs than at any time since the 2005 election. While the fall in Labour support gives the Tories a one-in-four chance of being the largest party in the House of Commons, it has only a five percent chance of winning an absolute majority.
In this month's polls support for Nigel Farage's Reform Party has risen five percent compared to its showing in the general election. This not only draws it closer to Labour in the 89 seats where it is second to the government, it it also reduces the Conservative lead over Reform by two percent. This leaves it on the wrong side of the barrier to winning lots of seats erected by the disproportional first-past-the-post electoral system. However, the barrier is lower than at the general election, when it won only 5 seats. Electoral Calculus estimates that Reform's vote share needs to be about 4pc ahead of the Conservatives for them to win more seats than the Tories.
Prof Richard Rose, University of Strathclyde, is Britain's senior election expert. He has been writing about elections at home and abroad for well over half a century.