The SNP and the Lib Dems should consider a pre-election pact

both parties would gain

I'll start with my thesis: the Scottish National Party and the Liberal Democrats would both gain from a pre-election pact at the next general election. To evaluate this first we'll describe what the SNP and Lib Dems want.

The SNP want indy

The SNP want independence. They also want Scotland to rejoin the EU, and they've been generally favourable to proportional voting systems such as the AMS system (used in Scottish parliamentary elections) and STV (used in Scottish local elections).

What do the Lib Dems want?

It has to be said that the Lib Dems are a unionist party -- that is, they want Scotland to remain part of the UK.

But in terms of other policies there's quite a lot of similarity between them and the SNP. The Lib Dems like STV. Their 2019 manifesto says:

Put an end to wasted votes, by introducing proportional representation through the Single Transferable Vote for electing MPs, and local councillors in England.

The Lib Dems have a long-standing commitment to a federal UK. Again, from their 2019 manifesto:

Liberal Democrats want home rule for each of the nations of a strong, federal and united United Kingdom. We have a proud record of leading the way on giving greater powers to Scotland and Wales. We will not allow Brexit to reverse devolution and will oppose attempts to use Brexit to go back to the past when powers were hoarded at Westminster. We will champion a federal future for the UK. Our plans for a written, federal constitution will include a permanent Scottish Parliament and National Assembly for Wales

While a federal UK isn't what the SNP want, from their point of view it's a step in the right direction.

These are not necessarily irreconcilable

While the SNP and the Lib Dems clearly want different things with respect to Scotland leaving the UK, I don't think their views are necessarily irreconcilable.

Arguably the best way to ensure Scotland stays in the UK would be a new constitution giving all the nations of the UK more powers, and parity of esteem. (By parity of esteem I mean that all 4 nations of the UK are treated equally, so that since Northern Ireland has the right to leave, then the other 3 nations need to have that right too. Also there needs to be a mechanism so that the UK doesn't just always do what England wants regardless of what the other nations want, which is what tends to happens because England has by far the largest population -- so there needs to be a balancing mechanism.) Such a settlement would guarantee that Scotland has the right to leave the UK if it pleases -- like Northern Ireland does as part of the Good Friday Agreement. If Scotland did have the right to leave the UK, then future Westminster governments would know they had to treat Scotland with respect, so would do so.

So the SNP and Lib Dems could conceivably come to an agreement, which might look something like this:

(1) allow a referendum on Scottish independence

(2) in that same referendum also include a question on more devolution (I've covered this previously).

Unite to Remain

Under FPTP small parties do badly, but by pooling their votes they could do better.

This was the motive behind the Unite To Remain pact in 2019, when the Lib Dems, the Green Party of England and Wales and Plaid Cymru had an agreement, under which they only ran one candidate between them in 60 constituencies.

This demonstrates that the Lib Dems are not opposed in principle to pre-election pacts.

Also in the 2019 European Parliamentary election, the Lib Dems offered a pact with the other pro-remain parties but were rebuffed. According to Wikipedia:

The three main nationwide pro-European Union parties standing in the election, Liberal Democrats, Greens and Change UK, wished to treat the election as a "soft referendum" on Europe. Commentators such as Marina Hyde raised the concern of a split vote among pro-Remain parties reducing the number of pro-Remain MEPs being elected. Vince Cable, the leader of the Liberal Democrats, proposed standing joint candidates with the Greens and Change UK on a common policy of seeking a second referendum on Brexit, but the other parties rejected the idea.

I think it was deeply stupid of Change UK and the Greens not to agree to a united pro-remain list, and confirms my opinion that politicians are often not the sharpest tools in the toolbox. In fact, some of them are as thick as two short planks (mentioning no names, and particularly not mentioning the name of Liz Truss).

will Liz Truss last longer than this lettuce?

How it might work

Ideally all the anti-Brexit parties should agree to the pact, and agree to stand just one candidate in every seat (at least, in every winnable seat). After the election, they will agree to negotiate jointly with the Labour and Conservative parties, offering confidence and supply in return for:

(1) a referendum on Scottish independence, with a devo max option

(2) a new constitution guaranteeing all constituent countries of the UK the right to leave that union

(3) all future parliamentary elections to be fought using a proportional system, such as STV (possibly with a referendum to confirm this)

(4) a referendum instructing the UK government to negotiate with the EU on rejoining that organisation, with the terms of such rejoining to be put to the people in another referendum

Prospects of Success

I think the prospects of success are very good, because:

(1) The Tories are very unpopular, but at the same time Labour have not won over the people. Thus people are looking for a third alternatives.

(2) Most voters are against Brexit, but Labour and the Conservatives are both for it. While Brexit won't be the only issues in the next election it will be clearly looming large in the background. And if the pro-Brexit vote is split but the anti-Brexit vote united, the parties that favour FPTP might end up being harmed by it, which would serve them right.

two cheeks of the same arse?

(3) In Scotland, Labour and the Conservative are vying against each other for who can be the most anti-Scotland and the most denying of Scotland's right to self determination. If the Lib Dems stood on a platform of "we don't want independence, but Scotland should have the right to secede if that's what they want" it would be seen as principled (something lacking in politicians)

(4) The prospect of lots of parties standing together under a common platform could excite the interest of many voters, who in their bones feel there is something deeply wrong with how Britain is governed and feel this might just be the change that would improve things.

(5) Looking at previous election results, the SNP won 56 seats in 2015 and 48 in 2019; the Lib Dems won 62 in 2005 and 57 in 2010. On similar form it's entirely possible that a Unite To Rejoin Alliance could win 100 or more seats, which would make a hung parliament very likely, unless the Tories have a complete meltdown (which is possible but I think unlikely).

Summary

In conclusion, the idea of a pre-election pact between the Scottish National Party (SNP) and the Liberal Democrats (Lib Dems) is not only feasible but also potentially beneficial for both parties. Despite their differing views on Scottish independence, there is a significant overlap in their policy preferences, particularly regarding proportional representation and devolution of powers. The success of the Unite To Remain pact in 2019 illustrates the potential benefits of such alliances, especially in a First-Past-The-Post voting system. A united front against Brexit could also be a compelling proposition for many voters.

The proposed pact could include a commitment to a referendum on Scottish independence, a new constitution guaranteeing the right to secede, a proportional voting system, and negotiations for rejoining the EU. Given the current political landscape, there is a real possibility that such an alliance could win a significant number of seats in the next general election, potentially holding the balance of power in a hung parliament. This could be a game-changer for the UK's political future.