For decades, a fixture of SNP campaigning were membership recruitment drives. Some, such as that led by the late Billy Wolfe in the mid-Sixties, attracted thousands of new members (including my father), others – particularly during the party’s long years on the fringes of politics – were only modestly effective.

All that’s changed since the emergence of the SNP as a party of government over the past decade. Shortly before last year’s independence referendum it had around 25,000 members, but in the weeks following the No vote, it more than doubled to over 50,000, making it the third largest party in the UK.

But it didn’t end there: by March 2015 the total had passed 100,000, meaning it entered the recent general election two-thirds the size of the Conservatives and half the size of Labour. That figure now stands at 115,000, meaning that around 1 in 50 of the adult population in Scotland is a member of the SNP – equivalent to the UK Labour Party having a million members.

This quadrupling in less than a year occurred without a concerted effort or strategy, although the creation of a centralised membership system when John Swinney was leader back in 2000-04, was an important reform. This removed the need for local branches to keep re-signing up members, thus liberating the party machine to concentrate on campaigning.

“Logistically in the mid-Nineties the party wouldn’t have been able to cope,” says an SNP insider of the recent dramatic growth in membership. “But after the referendum our technology helped greatly: most of the new members signed up online, so it then became a big processing job.”

But the party is also acutely aware it needs to keep hold of its 90,000 new members.

In that context a rolling cycle of elections helps. In less than a year’s time there will be elections to the Scottish Parliament, and after than an EU referendum and local government ballots. Social media also enables new members to feel involved, while they receive a weekly email from the party’s hugely popular leader (and Scottish First Minister) Nicola Sturgeon.

“By joining the SNP you can have a say in making Scotland all that it can be,” declares the party’s slick website, examples including voting for “the selection of parliamentary candidates and the party leadership”, and attendance at its annual conference and thus the opportunity to “take part in SNP policy making”.

The modern SNP, however, isn’t really much more internally democratic than its UK counterparts, and these days its two annual conferences are carefully stage-managed to avoid public dissent (an exception was the party’s 2012 debate over Nato). A motion at the most recent conference for the number of delegates to be scaled back was defeated, so they’ll continue to be large affairs.

“The activist base is very important to the SNP,” says a party insider. “The referendum showed how important local campaigning could be, as did the general election.”

And although Nicola Sturgeon is currently trying to play down talk of another referendum, the party knows how important its membership would be in a rerun of last year’s historic battle. “You need a lot of members to have a large campaign,” says the insider, “and although it would be bigger than just the SNP, we will always bring the bulk and numbers to another referendum.”

At the same time there are potential drawbacks to such a big influx of new members (although as Sturgeon once joked, it’s a “problem” she’s happy to have). Although the data is thin, it’s widely assumed many are significantly to the left of the SNP’s generally moderate leadership, perhaps more republican, and most likely more impatient for another independence plebiscite.

But, as the SNP insider points out, “almost everyone in Scotland will now know somebody who’s in the party; a member of their family, a colleague, or someone they know from bingo or bowling”. Not only will that “humanise” a party often caricatured by its opponents, it’ll help an already formidable campaigning machine cope with the electoral challenges ahead.