Party members remain vital for party campaigning: they are much more readily mobilized and engage more in high intensity activities than party supporters. However, there are more non-member supporters than there are supporters and they may be a significant organisational resource when most needed by parties.

It wasn't only pundits and the public who were caught completely by surprise by Theresa May's announcement of a general election in June.  So was her party - and all the other parties that will be trying just as hard as the Tories to defend and may be even to pick up seats in a few weeks time.  Whether they can do so depends, at least in part on their activists who deliver the so-called 'ground campaign'. But who are party activists today and what do they do when campaigning starts?

As in other Western democracies, until very recently in the UK the number of people formally joining parties, and who therefore traditionally provide the bulk of campaigning on the ground, has been declining. As a consequence, the role played at election time by party supporters (i.e. those who strongly identify with a party but who do not formally join it) has become increasingly important in complementing activities carried out by paying members. This has not been the only change in campaigning. The rise of new communication technologies and social media have led to increased online campaigning – most notably through social media such as Facebook and Twitter – alongside traditional tasks like delivering leaflets, putting up posters, attending meetings, canvassing voters and, for the most politically engaged, even standing for election.

Drawing on survey data collected for our ESRC-funded Party Members Project (PMP) (run together with Tim Bale and Paul Webb) following the 2015 UK general election, we have looked in more detail at differences and similarities in profiles and campaign activity between members and supporters of six British parties: Conservative, Labour, Liberal Democrat, the UK Independence Party (UKIP), the Greens and the Scottish National Party (SNP).

First, we looked at whether British party supporters are demographically different to members. As can be seen from Table 1, members are on average 51 years old, whereas supporters are 52. Although Greens activists tend to be younger and UKIP activists older compared to other parties, there are few age differences between members and supporters within the same party. However, party members are more likely to be male than their counterparts among supporters; indeed, except perhaps for the SNP, the differences are quite sharp in all parties. Party members are, on average, much more likely to be educated to graduate level than non-member supporters, with Labour, Liberal Democrats and Greens being the most highly educated, and Ukippers the least. Party members are also generally more likely to be from non-manual occupational grades than supporters: Liberal Democrats and Conservatives are the most middle-class, and once again, Ukippers are the least.

Then we looked at ideology. In terms of subjective self-location on the left-right scale, it is striking but perhaps not surprising that party members are, without exception, more radical (in the sense of being closer to one end of the ideological spectrum or the other) than their supporter counterparts: Labour, Green, SNP and even Liberal Democrat members all regard themselves as more left–wing than do supporters of their parties, while Conservative and UKIP members place themselves further to the right. The relative ordering of mean scores for the parties is identical within each of the samples: from left to right it runs from Green to Labour, SNP, Liberal Democrat, UKIP and Conservative.

When we look in detail at what activists actually do, the most striking feature of Table 2 is that, not surprisingly, full members of political parties are far more active on average than non-member supporters. To give an idea of the difference we can just look at the two most widespread activities: liking something posted by the party or by a party candidate on Facebook and displaying election posters in one’s window. The online activity was carried out by about half of the members (53%), as opposed to a fifth of supporters (21%), whereas the offline activity was carried out by almost half (46%) of the  members and a tenth of supporters (10%). This difference is especially noticeable when it comes to more intensive forms of activity – things like leafletting, canvassing and even standing for elected office. Thus, on the whole, party members remain vitally important campaign resources for political parties and much more active that party supporters.

While this is true when we compare the relative rates of activity undertaken by these two groups, the story is quite different when we consider the overall impact of that activity on election campaigns at the aggregate level. Notwithstanding supporters’ much lower rates of campaign activity at the individual level, British parties, as is the case throughout Western democracies, attract far more supporters than members. This suggests that they may benefit hugely from party identifiers because of their sheer number. By using data from the British Election Study to gauge (a) the number of strong party supporters out there in the electorate and creating (b) an activism index (a measure of how many of the campaign activities on offer that each person undertook), in Table 3 we can – by subtracting the number of members from (a) so as to avoid double-counting and then multiplying (a) by (b) – estimate supporters relative contributions in 2015.

What is clear is that there are far more strong supporters in the electorate than there are party members. As a result, except for the Green party, the sum total of campaign activity undertaken by party-supporting non-members is at least as great if not greater than that of party members. Labour in particular seems to have benefitted from the input of non-member supporters in 2015, although the balance between the two groups might be different now that around half a million people are fully paying members of the party. The same goes for the post-Brexit and post-2017 GE announcement Lib Dem surges.

In short, on the one hand our analysis suggests that the contribution by party supporters should not be underestimated by parties since, at the aggregate level, they may constitute a significant organisational and human resources when most needed by parties. Supporters have also a more equal gender split, and they are on average less well-educated and more likely to be in manual-occupational grades than party members, making them more likely to be representative of the average voter. On the other hand, however, party members remain vital for party campaigning. Not only are they much more readily mobilized into the high-intensity activities vital to electoral mobilization than are party supporters. But they might well be important, too, as facilitators and motivators of the efforts of those who are willing to volunteer their time to campaign for the party they support even if they haven’t gone so far as to actually join it.