Handled with caution, the answer is: a few big points. Caution is needed because local government is responsible for pot-holes not the state of the economy. Moreover, because six times as many councillors are elected as MPs, parties can win wards but have their support swamped when votes are counted at the much bigger level of constituencies. Because the results will be bad for Labour, this will confirm that a general election is more than 156 weeks off, and that's a long time in politics.
Nonetheless, the evidence produced by next Thursday's elections in England, Scotland and Wales will represent the opinions of millions of voters. Moreover, MPs at Westminster will be faced with premonitions of what might happen to them when voters hold them personally to account for what their party has accomplished at Westminster when the next general election comes.
Whatever the scale of Labour's losses, they will bad for Labour and consistent with Electoral Calculus' prediction that Labour would come third if a general election were held today. Dispirited ex-councillors and local party members will put pressure on their MP to do something to stop the party haemorrhaging votes. Changing the party leader is the readiest action that can be taken.
The Greens will make a breakthrough by winning hundreds of council seats. In London Zack Polanski's rebranding of the party as left-wing will cost Labour control of some boroughs and it may emerge as the larger party in some councils. MRP predictions show that the Greens could take enough seats from Labour at a Westminster election to push it into third place behind both Reform UK and the Conservatives.
Labour is also threatened in Birmingham and Bradford by a quadrupling of Muslim candidates standing as independents. They appeal to their co-religionists for votes not only by supporting Palestine but also by arguing that Labour should not take the votes of Muslims for granted.
Conservatives can rationalise the results as not as bad as last year or as Labour's loss. However, if the Liberal Democrats overtake the Conservatives as the second largest party in local government, this will have a ripple effect in Westminster. Opinion polls are showing the Tories are hard pushed to come second in the national vote. Moreover, current polling predicts that the Tories could have even fewer MPs at the next election than they took when suffering their worst defeat in history at the last election.
Whether Reform UK gains 1,000 or 2,000 council seats it will be the big winner overall, because it did not exist when these council seats wre last contested in 2022. This will give many novice Reform politicians a chance to show their potential as parliamentary candidates. It will also test how well the party's new system for vetting candidates has succeeded in screening out rogues. Reform's breakthrough will also test the pariah policy of established parties In councils where the only alternative to Reform taking control of a council is a Labour-Conservative-Liberal Democrat pact.
In the Scottish Parliament election, the hope raised by Keir Starmer's victory two years ago will be crushed. The Scottish Labour leader has already called for Starmer to leave Downing Street. The chief uncertainty is whether the Scottish National Party will win an absolute majority or fall a few seats short. If the latter happens, the SNP could keep control of Scottish government in the absence of all the Union parties and Scottish Greens combining to vote against it.
In the Welsh Senedd election, polls have Plaid Cymru and Reform competing for first place and Labour trailing far beyond. Seat projections show a hung Senedd. Thus, the formation of a coalition government in Cardiff will preview the challenge that British parties face at Westminster. It would take a five-party anti-Reform coalition to form a parliamentary majority if a general election were held today.
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 on 9 June.