In Glasgow this morning, the new Scottish Labour leader Richard Leonard will join Jeremy Corbyn to outline their “positive” vision for Scotland.

Labour leaders, of course, have done that many times before, but Leonard’s political “offer” will represent a break with Blairite orthodoxy: federalism, higher taxes, closer trade union links and the renationalisation of rail and buses.

This might be called the politics of differentiation, the realisation that modern campaigning rests upon presenting voters with a clear political choice, one that might often be more rhetorical than real, but a choice nevertheless.

For the past decade, the SNP has pursued this strategy with panache, not only at the 2007 and 2011 Holyrood elections but at the 2014 independence referendum. Almost everything the Scottish Government did was contrived to present a clear contrast between progressive Scotland and right-wing England, between the pro-Scotland SNP and “anti-Scotland” Unionist parties.

Yesterday Leonard even praised the pro-independence campaign of 2012-14 for having “put forward a vision of a different kind of Scotland”, something he suggested the Scottish Labour Party should ape between now and the 2021 Holyrood election. And, unfortunately for the SNP, Leonard will find that easier to do than Anas Sarwar might have, someone who would have been framed as “same old, same old” by Nationalists.

But not only is Richard Leonard gearing up for a clear differentiation between his agenda and that of the SNP (who he’ll depict as being as much in thrall to the capitalist status quo as the Tories) so, remarkably, are the Conservatives both north and south of the Border, aided by a growing list of policy divergences.

Last week’s Budget was awash with the politics of differentiation, chiefly as a result of further reforms to stamp duty in England and the Scottish Government’s plans for income tax reform. The refrain from Hammond et al is that Scotland is, and will continue to be, the “highest taxed” part of the United Kingdom. Now the SNP will dispute this, pointing out that Scottish taxpayers enjoy several “free” services, but in politics it’s the impression that counts. Never before has the Scottish Government been urged to follow England’s lead rather than reject it.

Long cynical about nationalist depictions of Scots as egalitarian types willing to pay higher taxes for better public services, the Scottish Conservatives are now looking forward to testing that (always simplistic) thesis to destruction. “Differentiation is vital in politics,” reflects a senior Scottish Tory. “Why should you vote for someone? It’s about a clear choice, and as we move towards 2021 the choice between Ruth Davidson and Nicola Sturgeon will relentlessly be our message.”

Ironically, the SNP continues to hand their Tory enemies differentiation gifts on a plate. In March, though it’s now easy to forget, Nicola Sturgeon called for a second independence referendum, allowing the Conservatives to present themselves as unequivocally opposed to more constitutional upheaval, while the First Minister’s decision to forego a Treasury increase in the upper rate threshold allowed Ruth Davidson to campaign on income tax too.

In case no-one’s noticed, Conservatives like campaigning against independence and higher taxes which, for the first time in the past 20 years, has given the party a clear stance within the once heavily-centrist Scottish political system, one they intend to augment with a clearer domestic policy agenda focusing on housing, health and education.

The “tax burden” debate cuts across a number of SNP arguments. How, for example, is the Scottish Government intending to attract more GPs to Scotland when they’re likely to end up paying more tax than in other parts of the UK? One way to take the wind out of Tory sails, however, would be to cut income tax for lower earners while raising it for those on higher incomes. That’d be clever politics, although it probably wouldn’t end up raising very much additional revenue which, after all, is the whole point.

Scottish Tory strategists, meanwhile, point to two recent council by-elections as evidence of what they call an anti-SNP “squeeze” now that Labour and the Conservatives appear more credible alternatives to the governing party. Not only did the Tories hold a Perth ward in difficult circumstances, but in South Lanarkshire Labour held on to another council seat with a big swing away from the SNP.

Sure, it’s sensible not to over-analyse local authority by-elections, but these two results add to general evidence of a squeeze, not to mention anti-SNP tactical voting, another new experience for the party. Nationalists clearly sense this and don’t much like being on the defensive, as has increasingly been the case since early 2016. For about a decade they’d had the wind to their back, and now it’s in their face they don’t seem to be coping very well.

The election in June of 13 Scottish Tory MPs (rather than just one) was significant in this respect. Prior to the “snap” general election, Scottish Secretary David Mundell was limited in how proactive he could be in attacking the Scottish Government, but now he has a dozen colleagues to help him out, the best of which know exactly how to get under the SNP’s skin.

On Brexit, however, differentiation is much harder. Not only do the UK Tory and Labour parties essentially agree (beyond how long a “transitional” period ought to last), but the SNP appear to be tempering their pro-EU stance, conscious it doesn’t go down well with Leavers in their own camp.

Richard Leonard, meanwhile, appears to be positioning Scottish Labour as the party of a “soft” Brexit in order to compete with the SNP, although his more immediate challenge as leader will be getting noticed, especially when he’s up against two big personalities called Nicola Sturgeon and Ruth Davidson. “We,” declares a senior Scottish Tory, “will be working very hard to make sure Leonard doesn’t get a look in.” The differentiation game is afoot.