1. Boris Johnson’s Conservatives would start any election campaign with an advantage.

Johnson’s strategy since entering Downing Street has been to try to unify the leave vote by taking a hard Brexit approach, while hoping that Jeremy Corbyn cannot unite remain voters to the same degree.

That appears to have been effective: polling averages show the Conservatives up at around 33%, having taken share from the Brexit party, while Labour is stalled at 25% and the Lib Dems are holding up at about 18%.

2. This could translate into a Conservative majority – although not all pollsters agree.

Electoral Calculus estimates, based on an analysis of polling from 26 July, when Johnson became prime minister, to 31 August, that the Conservatives would win an overall majority of 62.

The prime minister’s party, with 33.3% of the vote, would win 356 seats, while Labour, at 25%, would take 188. That comes despite the SNP reasserting its dominance of Scotland taking 50 out of 59 seats. The Lib Dems, meanwhile, would win 34 seats.

But this forecast rests on the assumption that Johnson can make real inroads into traditional Labour seats in the Midlands and north with his Brexit “do or die” strategy. Other pollsters are more sceptical.

Polling conducted by Focus Data, on behalf of pro-EU Conservatives and released overnight, concludes that the Conservatives would only end up with 311 seats, well short of the 326 needed for an overall majority in the Commons, although Labour would also lose ground with 242.

More interestingly still, if the pro Brexit DUP retained its 10 seats that would leave pro-Brexit parties on 321. The combined opposition, meanwhile, could reach the same figure: taking Labour’s 242 plus 52 for the SNP, 21 Lib Dems, four Plaid, one Green and Lady Sylvia Hermon, the independent MP for North Down, who has said she is against no deal. A parliament as divided as the current one.

3. Last time, Theresa May lost a 21-point lead, but it is not as clear that Labour can pull off the same comeback again.

May started the 2017 campaign looking like a winner, but she turned out to be a hopeless performer, while Labour’s anti-austerity and pro-nationalisation policies proved an unexpected hit with the electorate.

Few believe, however, that Johnson could be as poor a campaigner as May and while the prime minister divides opinion, recent YouGov polling has him ahead of Corbyn on most personal metrics. Johnson is rated as incompetent by 43% of voters; Corbyn, however, scores 66%.

That could change rapidly however. Johnson’s decision to suspend parliament early has not proved popular and his uncertain, fast talking address outside Downing Street showed that he too can be rattled.

4. Nigel Farage could end up as kingmaker and the Brexit party’s final share will be critical.

Ultimately Johnson only has to defeat the Labour party. But his Conservatives must dramatically reduce the Brexit party’s share. Farage’s party is polling at anywhere between 12% and 16%, support that would otherwise go to the Conservatives.

Squeezing its vote is critical, or Johnson risks a repeat of the Peterborough byelection on a national scale, where Labour won because the leave vote was split.

There remains the possibility that Farage could pull out. The party leader claimed he would help Johnson’s Conservatives if the prime minister embraced a no-deal Brexit. But would such a rightwing coalition be popular? Polling suggests a majority of Britons remain opposed to a no-deal Brexit, by 46% to 37%.

5. The situation remains incredibly volatile.

It has become a feature of contemporary politics to be dismissive of polling. The reality is that the dynamic of an election campaign has become critical, particularly one that will be set against the backdrop of the Brexit crisis.

In 2015, English voters were successfully frightened by the idea of a Labour-SNP coalition – an idea that was pushed out by the Conservatives at a point when voters believed the outcome would be a hung parliament.

In 2017, Labour outperformed expectations in an election where Brexit was not the issue. This time, Brexit is the dominant issue and Corbyn has to pick up remain voters currently inclined to the Lib Dems and simultaneously rouse Labour’s traditional working-class base if it is to succeed.