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)