Mr Johnson wants to demonstrate that the ‘Partygate’ row has not inflicted serious damage on his party. Ms Sturgeon will be hoping the result will give her some political momentum as she pursues her quest to hold a second independence referendum.
As it happens, both might be in luck.
True, the Conservatives have been behind in the GB-wide polls since the Partygate row first exploded before Christmas – the first time the party has been behind since Mr Johnson won an 80-seat Commons majority in 2019. The Conservatives, on 34 per cent, currently trail Labour by six points.
But even if the party’s poll position is replicated in the local ballot boxes, this will not, in England at least, generate headline-grabbing heavy Tory losses of council control and seats.
Most of the seats being contested south of the Border were last fought over in May 2018, when Theresa May was struggling to deal with a loss of authority following her failure to secure an overall majority in the 2017 general election.
At the time, the Conservatives were just two points ahead in the polls, while the BBC’s estimate of what would have happened in a general election if voters had behaved as they did in the local elections put the Conservatives and Labour neck and neck. It was Labour’s best local election performance under Jeremy Corbyn’s leadership.
Consequently, even if the polls are correct, there could be no more than a three-point swing from Conservative to Labour on Thursday – enough to produce some Conservative losses (to the Liberal Democrats as well as Labour) – but not a tsunami.
Not all of England is voting on Thursday. While the whole of London will be going to the polls, outside the capital it is, for the most part, only the more urban councils that are holding an election. As a result, it is Labour, not the Conservatives, who have most at stake.
London is now dominated by Labour – the party won 44 per cent of the vote last time and secured control of 21 of the 32 boroughs. The Conservatives were left with just 29 per cent of the vote and command of just seven boroughs. Labour will be defending 1,140 seats, the Conservatives less than 500.
Even outside London, Labour currently control as many, 41, of the 114 councils at stake as the Conservatives, 39, while Labour will be defending nearly 1,100 seats to the Conservatives’ 900.
Moreover, whereas in London all of the seats on each council are up for grabs, outside the capital in most cases only one-third (or occasionally one-half) of the seats are being contested. In many instances where the Conservatives are in control, too few of the party’s seats are at risk for it to be likely to lose control.
Consequently, the party is unlikely to lose many councils. True, they may include Wandsworth, which has become a Tory icon following repeated success, since 1978, at beating back a Labour challenge on the back of one of the lowest council taxes in London. Losing it would hurt.
But otherwise, even in London, only one other Tory-held council, Barnet, looks at serious risk given the current polls. Labour should have won there in 2018, but in a borough with a high proportion of Jews the party’s support was eroded by the anti-semitism row that surrounded Jeremy Corbyn. It will only be bad night for the Conservatives if the losses extend further to Westminster or Hillingdon.
Outside London, Tory losses of control could prove just as scarce. Southampton and Newcastle-under-Lyme might fall, while, Monmouth, the one council the party is defending in Wales (where there are elections for all seats on the country’s 22 councils), looks vulnerable. But the final list may not prove much longer than this.
The elections in Scotland, however, might present Mr Johnson with more of a challenge. Here all 1,226 seats on the country’s 32 councils are at stake. The ballot is being held using the single transferable vote system of proportional representation, as a result of which none of the parties currently control a single council.
The last elections were held not, as in England, in 2018 but in 2017, when the Conservatives were riding high in the polls (on the back of which Theresa May had already called the 2017 general election). This was reflected in the Scottish Tories’ best local election performance since 1982.
Now the party is having to defend this high-water mark, against the backdrop of a much lower poll rating that has been further eroded by the Prime Minister’s travails at Westminster. Recent polls have consistently suggested that the party has fallen behind Labour in the battle for second place. Such an outcome would represent a notable rebuff for the Prime Minister.
The SNP, in contrast, registered a relatively disappointing result in 2017. It did no more than retain the 32 per cent support it had won in 2012, before the party had swept all before it in the 2015 UK election. Indeed, this seemingly modest performance appeared to presage the substantial loses the party suffered in the general election a few weeks later.
In theory, this gives Ms Sturgeon a good chance of registering an increase in her party’s support and thereby gain some political momentum. The party might gain control of Dundee, lost in 2017, though getting over the line in Glasgow looks more difficult.
However, the SNP’s average standing in the current polls is only on a par with where it stood five years ago, so an advance is by no means guaranteed.
Both Ms Sturgeon and Mr Johnson, appear to be batting on a favourable wicket on Thursday. Nevertheless, there will still some nail-biting in Bute House and Downing St on Friday.
John Curtice is professor of politics, Strathclyde University, and senior research fellow, ScotCen Social Research