Millions going to polls for unusually significant elections on Thursday

Voters go to the polls on Thursday in unusually crucial local and devolved elections, which could have a decisive influence not only on Boris Johnson’s position as prime minister but also on the future of Northern Ireland and the Brexit agreement.

The ballots, taking place in all four nations of the UK, represent the first opportunity for voters to cast their verdict on Mr Johnson following the Partygate affair, and some Tory MPs are known to be waiting for the result before deciding whether to join the bid to oust him as leader.

And a historic change is expected in elections to the 90 seats of the Northern Ireland assembly, where polls suggest nationalists Sinn Fein are on track to become the largest single party for the first time since the institution’s creation in 1998.

Victory for Mary Lou McDonald’s party would provoke a constitutional crisis in the country, with the unionist DUP refusing to say whether it would nominate a deputy first minister to serve alongside Sinn Fein’s Michelle O’Neill as first minister, as required by the Good Friday Agreement.

Failure to do so would trigger months of political wrangling, and would spark demands to reopen the agreement for the first time since 1998 in order to reconsider the power-sharing provisions that were designed to ensure joint unionist and nationalist community representation in the executive.

And, while there is no question of a border poll any time soon, as unionist parties will between them constitute a majority of MLAs (members of the legislative assembly), nationalists will see the results as a crucial step on the road to their overall goal of reunion with the Irish Republic.

The resultant turmoil is also likely to hike up pressure on Westminster to make good on its threats – backed by the DUP – to tear up the Northern Ireland protocol, agreed by Boris Johnson as part of his Brexit deal, by invoking Article 16. Doing so would risk a trade war with the EU.

Meanwhile, Mr Johnson’s own position may be at stake if the Conservatives perform poorly in council elections across England, Scotland and Wales, as well as those being held in seven directly elected mayoralties, in South Yorkshire, Croydon, Hackney, Lewisham, Newham, Tower Hamlets and Watford.

The fiercest battles are expected in London, with Labour hoping to seize control of Barnet and Wandsworth councils, though there is an unpredictable element thanks to furious local rows over low traffic neighbourhoods, an innovation designed to cut car use.

But the distribution of seats being contested makes it unlikely that many councils will change hands in England, with interest focused instead on whether Sir Keir Starmer’s party can make inroads in the red-wall areas of the Midlands and the north of England, where the Tories seized a string of parliamentary seats in 2019. Labour is eyeing seats in towns such as Bury, Dudley and Walsall.

Meanwhile, the Liberal Democrats are looking to leader Ed Davey’s promise to smash through the “blue wall” of traditional Tory dominance in the home counties, leafy suburbs and rural England, hoping to pick up councillors in Richmond and Merton in London, Elmbridge and St Albans in the capital’s commuter belt, and Harrogate in the north – now part of the new North Yorkshire unitary authority.

In Scotland – where all 32 local authorities are facing re-election – all eyes are on Nicola Sturgeon, to see whether her faltering recent performance translates into lost seats for the SNP.

Polls suggest a difficult night for the Conservatives, with Partygate fines and the recent loss of a brace of MPs in sex scandals undermining advances made in light of Mr Johnson’s well-regarded handling of the Ukraine war.

But the Tory leader’s hopes of persuading MPs to stick with him are bolstered by the arithmetic of Thursday’s votes, as Labour performed relatively well the last time most of the English wards at stake were contested in 2018, with Jeremy Corbyn at the height of his popularity and Theresa May mired in Brexit woes.

With Tories holding only 1,200 or so of the approximately 6,800 seats up for election in mainland Britain, even a very poor night for Mr Johnson might result in only 350-500 lost councillors, and a catastrophic one in the loss of 800.

Conservative MPs who said they would wait for the verdict of voters on Thursday before deciding to throw their lot in with rebels who have declared no confidence in their leader are now thought to believe it would be better to wait a little longer – until the completion of the Metropolitan Police inquiry into the Downing Street parties, and the report of senior civil servant Sue Gray.

So Thursday’s elections – as well as deciding who will have responsibility for libraries and potholes and cycle lanes – are likely to hammer another nail into Mr Johnson’s coffin, while still allowing him space to scramble his way free.

And they will give a pointer towards whether Keir Starmer is starting to reverse the historic reshaping of the English political landscape in 2019, and whether there are any chinks of light appearing for him in Labour’s long Scottish nightmare.

But most significantly, they are expected to mark a historic step in the peace process in Northern Ireland, with highly unpredictable results.