This week's briefing provides a short General Election primer. All data, odds and polls are correct as of 7pm on Sunday 4 June.
Voting in Thursday's election will take place between 7am and 10pm. The counting of ballots will begin as soon as the polls have closed.
The final result will be confirmed on Friday morning but from 10pm exit polls will give an early indication of the result. Exit polls, usually commissioned by each of the major broadcasters, proved extremely accurate in the 2005 and 2010 General Elections. In the 2015 General Election the BBC's exit poll provided dramatic evidence of a Conservative win, contradicting the pre-election polls.
The first official result is usually declared before midnight and if it is a clear victory for one party the result is likely to be apparent by about 3am. For the last six general elections one of the three Sunderland constituencies has won the race to declare the first result. In 2015 the result from Houghton and Sunderland West was announced just 48 minutes after the polls closed.
The election campaign has delivered a number of surprises, most obviously the strong revival in Labour's poll ratings. Although voters say that leaving the EU is the most important issue facing Britain, Brexit has not proved as dominant an electoral issue as most of us expected. And rather than gaining support from pro-EU voters the Lib Dems' share of the vote has edged lower since the election was announced on 18th April. UKIP's poll rating has halved since the middle of April.
Recent months have seen an unwinding of the trend towards smaller parties gaining ground at the expense of the two main parties. UKIP's current vote share, of around 5%, compares with the 27% of the vote the party took in the 2014 European elections. The Lib Dems' current poll rating of 9% is down from the peak of 23% achieved in the 2010 General Election.
The latest polls show the Conservatives and Labour jointly accounting for about 80% of the UK vote, the highest level in more than five years.
In the latest six polls Labour stands on 37% of the vote, up from 26% at the start of the campaign. The main source of Labour's poll surge seems to have been defections from UKIP and the Lib Dems. In the 2015 General Election, under Ed Milliband, Labour secured just over 30% of the national vote.
Mr Corbyn's personal approval ratings have picked up strongly in the last fortnight. His approval rating stands at 39%, higher than his party and higher than that of Ed Milliband at the time of the 2015 General Election.
Mrs May's approval rating has suffered, dropping to 43% from 55% in May. Her popularity is at similar levels to her party, having previously been well ahead. The latest six polls put the Conservatives on 43%, unchanged since the start of the campaign. This compares with the 37% share of the vote secured by the Conservatives under David Cameron in 2015.
Last week's big surprise was the You Gov poll-based prediction of a hung Parliament – compared to a current Conservative majority of 16 and speculation at the start of the campaign of a Conservative landslide.
You Gov is updating its election model daily and the results on Sunday predict a hung parliament with the Conservatives as the largest party on 308 seats. Labour, on a predicted 261 seats, with the support of a forecast 47 SNP MPs and 10 Lib Dems, would still be 8 seats short of a Parliamentary majority.
You Gov's findings hinge on a high turnout by younger voters. Most other pollsters' assume a lower youth vote which would deliver a better showing for the Conservatives. Thus most sources point to a Conservative majority.
Martin Baxter at Electoral Calculus combines data from all the opinion polls to model the distribution of seats. His latest projections, based on opinion polls from 25th May to 3rd June, give the Tories a 72-seat majority.
The bookies also expect a Conservative majority. PaddyPower's current betting odds imply an 82% probability of the Conservatives winning a Parliamentary majority. The IG spread betting index shows that punters expect the Conservatives to secure a majority of around 82 seats. Of course the betting markets, like the polls, get things wrong as was proved, quite spectacularly, by the EU referendum and the US election.
So the weight of data and forecasts point to a Conservative majority. Yet that majority is expected to be smaller than a month ago and betting markets see a low, but growing possibility of an outright Labour majority or a hung Parliament. As of Sunday evening the implied probability of Labour winning a Parliamentary majority was 6%, according to PaddyPower's odds, and the probability of a hung Parliament stood at 23%.
The outcome of this election is looking a lot less clear cut than a month ago. On past form the exit polls should give a rough idea of the outcome shortly after 10pm on Thursday. Those wanting a fuller picture of will probably need to stay up for a further four-to-five hours.
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