Three weeks from election day – how much could the polls change?
Exactly three weeks from today, millions of people across the UK will be voting in the General Election.
Opinion polls continue to suggest the Conservative Party enjoys a strong lead over Labour.
The latest poll averages put the Tories on 43%, with Labour on 29%, the Lib Dems 14%, the Brexit Party 5% and the Greens 3%.
What is the likelihood of the polls shifting decisively between now and election day?
At this point in the 2017 election campaign, the polls showed the Tories on 47%, with Labour on 31%, the Lib Dems on 8%, Ukip on 5% and the Greens on 3%.
But on election day, the Tories finished on 43% – four points below where they had been three weeks earlier – while Labour had risen 10 points to 41%.
While the Lib Dems remained on 8%, both Ukip and the Greens dropped to 2%.
The change was enough to deny the Tories a majority and produce a hung parliament.
There was movement in 2015 as well, albeit on a smaller scale and with different consequences.
Three weeks before polling day in 2015, both the Tories and Labour were averaging 34% with Ukip on 13%, the Lib Dems 8% and the Greens 5%.
These figures pointed to a hung parliament – but come election day, the Tories opened up a seven-point lead over Labour to finish on 38% while Labour ended on 31%.
Ukip, the Lib Dems and Green finished on 13%, 8% and 4% respectively.
This was enough to give the Conservatives a small overall majority in parliament.
The pattern in 2015 and 2017 suggests a lot can change in the three weeks before polling day.
It also serves as a reminder that polls are not predictions, merely snapshots of opinion at a certain point in time.
(Note: all figures quoted above are for vote shares in Great Britain)