Tory MPs have now voted five times to narrow the field of their leadership race down to just two candidates. Rishi Sunak and Liz Truss will go head-to-head, and the winner will replace Boris Johnson as prime minister.
Unlike the previous rounds, however, this one has a broader electorate: Tory members will get to vote on which of the pair becomes party leader.
We can expect to see the tenor of the race shift as candidates try to appeal beyond the parliament party, and to the membership in general. But who are these people?
We do not know how many Conservative party members there are, because the party has stopped releasing official figures.
But we know there were at least 160,000 people in the party when Boris Johnson became PM. This is because that is how many people were eligible to participate in the last leadership contest in 2019. The party says this figure is likely to be higher this time.
Where do they live?
One useful resource for understanding party membership is the Economic and Social Research Council's Party Members Project, run by academics Tim Bale, Paul Webb and Monica Poletti.
The latest figures the project has on Conservative party membership suggests that the member will largely be chosen by people living in London and the south east.
As of January 2020 the project determined that a full 56 per cent of Tory members live in London and the south east. Just 18 per cent live in the Midlands, 20 per cent in the North of England, and 6 per cent in Scotland.
This may go some way to explaining why leadership candidates have not talked much about the government's supposed flagship "levelling up" policy. That is aimed at voters in marginal seats they need to win in general elections, not people taking part in leadership contests.
What's their background?
One thing that stands out about Conservative party members, according to the Party Members' Project data, is that they are overwhelmingly male. 63 per cent of Tory members are male, compared to 37 per cent who are female.
They also skew older: just 6 per cent of the membership is under 24-years-old, while 36 are aged 25 to 49 years old. The majority after 50 and older: 19 per cent between 50 and 64 years old, and 39 per cent over 65.
The members are also generally middle class. 80 per cent belong to the highest social economic group, ABC1, which is used by marketers to denote different backgrounds. This should be considered a rough guide, as NRS social grade system has been the subject of criticism in recent years.
Perhaps more interesting is the fact that 40 per cent of Conservative members earn more than the national average, and one in 20 earns more than £100,000. This is particularly notable given about 4 in 10 are eligible for their pensions.
Data published by the same academics found 97 per cent of Tory members are white, somewhat out of step with the general population where 87 per cent of the population are white.
It should be noted that all political parties have a omewhat middle class, white, and older membership - though according to these figures the Conservative party is the most middle class, the most white, the oldest, and particularly the most male.
What are their political beliefs?
This is a matter of some debate, and difficult to quantify. Generally, however, it seems clear from the data that Tory members' views are somewhat closer to the rest of the British public than at least the most outspoken Conservative MPs.
Take views on climate change: a survey by Opinium earlier this month found that just 37 per cent of Conservative members believe the UK government is "overreacting" on climate action, with 22 per cent saying it is underreacting and 30 per cent saying it it is getting policy about right.
Boris Johnson and Brexit merchandise for sale at the Tory conference
This is in market contrast to the furore among some Tory MPs pushing to scrap net zero. While other surveys have shown climate well down the priority list for members, there is little in the way of active antipathy to climate action.
A similar picture can be seen on the size of the state – a question which seems to preoccupy Tory MPs. In the early rounds of the leadership contests, candidates sought to emphasise the huge tax cuts they would make to win votes.
But this, too, is not something members are nearly as ideological about. Opinium found that just 29 per cent of Tory members want less tax or spending, with 20 per cent saying they want more. 38 per cent say the balance should stay as now.
On the issue of Brexit, however, members are where you might expect them to be: just 24 per cent backed Remain in the EU referendum, with 76 per cent supporting a Leave vote.