Who will pose with the penguins now? Who will sit in the giant deckchair? Who will zip-wire, and water-ski, and star-jump? Willie Rennie, leader of the Scottish Lib Dems and lover of a colourful photo opportunity, has revealed that he’s standing down and, true to form, he made the announcement from the top of a hill, apparently unaware – or no longer caring – about the metaphorical significance of a politician standing at the top of a steep downward slope.

And let’s be honest anyway: if judged solely on election results, it’s been downhill all the way for the Lib Dems under Mr Rennie’s leadership. When he took over, the Lib Dems, and Labour, had just suffered the terrible defeat of 2011 amid the SNP surge. But since then, Mr Rennie's party has sunk even lower, losing another Holyrood seat in May. As for Westminster, it’s even worse: the party had 57 seats ten years ago; now it’s 11.

I’m not suggesting Mr Rennie is entirely, or even mostly, to blame for the Scottish situation: the trends that led us to where we are now – the economic crisis of 2007, the decline of Labour, the ascendancy of Alex Salmond – all of those were in place before he took over. But ten years on, liberalism no longer seems to be able to rely on the place it once had in the Scottish political and psychological landscape, and I think it’s fair to ask what part the Lib Dems have played in that.

The answer is probably that they've done their best. Mr Rennie is ebullient and likeable, although at times, on independence, he hasn’t always sounded particularly liberal. During the election in May for example, he said he wouldn’t support a second referendum under any circumstances at any time, which, even for someone as passionate about the UK as Mr Rennie, sounded a tad illiberal. Liberals must surely accept that Scotland’s membership of the union is by consent and, occasionally, the consent needs to be tested.

But the bigger problem is that liberalism, particularly the common-sensical variant Mr Rennie represents, has been squeezed by a number of unpleasant trends. The first is the rise of me-politics: politics based on personal identities, be it sex, race, sexuality or even age. It’s much harder for a liberal who talks about commonality to thrive when everyone is talking about difference.

The rise in nationalism has also been a problem for Mr Rennie, which he acknowledged in his resignation speech. Scotland, he said, is lumbered with twin nationalisms – one represented by the SNP, the other by the Tories – and an alternative is needed. But again, it’s hard for a nice chap like Mr Rennie to find a way through when everyone is ranting about nationalism and you’re staging photo ops that, frankly, seemed better suited to the age when people mainly saw politicians on the TV news patting dogs and kissing babies.

However, none of that means Mr Rennie’s diagnosis – that we need an alternative to the two extremes – is wrong. Quite the opposite: the idea of building a liberal consensus in the middle of politics will sound like a good idea to anyone still suffering post-2014 fatigue. And there’s no doubt the consensus does still exist, and is prepared to be convinced, even though it’s the two extremes that make the most noise.

The other interesting question is where the consensus might lead, and whether some Yes supporters could feel part of it. I remember talking to the former Lib Dem leader Jo Swinson about this and she pointed out that devolution in the 90s was the end result of a long period of engagement by all the parties, from which a consensus emerged (bar the Tories). The result was a referendum in 1997 that effectively confirmed a settled public opinion.

Ms Swinson’s view was that we need to do the same again and build a new settled will on the constitution and a new leader of the Scottish Lib Dems could promote that idea. He or she would need to point out that it will take time (so no second referendum any time soon). But the bigger point is that no one is dictating where the consensus might end up. It could be No. But maybe not. Maybe a new, liberal consensus could, in the end, lead to Yes.

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