Scottish Secretary David Mundell has been in Holyrood today to meet, among other people, the SNP Deputy First Minister, John Swinney.

Mr Mundell, the Tory MP for Dumfriesshire, Clydesdale & Tweeddale, was looking remarkably chipper.

As the only Scottish Conservative MP, swamped by the massed ranks of the 56 MPs elected under the SNP banner in May, you'd think he'd be constantly beleaguered.

Mr Mundell does not give that appearance. Why? One reason could be that he's been reading the newspapers today, the day after Mr Swinney's budget announcement.

It would be fair to say that with local authorities railing against a cut of some £300 million or more in their budgets, the headlines are not exactly positive for the finance secretary.

For any politician of any political stripe your opponents discomfort is always welcome. If they're getting a hard time it is less likely that you will be.

But there might be sometime a bit deeper in the quiet Tory pleasure at the post-budget tidings of festive discomfort and despair for the SNP.

For the Conservatives, the fact Mr Swinney had to decide whether to raise 10p in the pound worth of income tax forces the SNP - finally in the Tory view - to take a big decision, and one with consequences.

Even though the Deputy First Minister chose not to put up, or reduce, the 10p rate, he is facing criticism over his stance.

Mr Swinney claimed that the tax powers he has now, which force him to put up the rate on all three tax bands by the same amount (that is accurate), would disadvantage basic rate taxpayers disproportionately.

Nicola Sturgeon repeated this at First Minister's questions today, saying the SNP would not adopt a tax policy that would hit the less well off in Scotland the hardest, and advantage the better off.

But is this correct? Professor David Bell of Stirling University disputed this claim in an interview I did with him for Representing Border last night.

A respected economist, who has advised Holyrood committees, Prof Bell told me if tax was put up across all three bands the money raised could have been used to help poorer people.

In other words the SNP could have used this tax, and the money raised, to be what they claim to be a party of 'progressive' taxation.

Professor David Bell of Stirling University believes raising income tax will not disproportionately affect the disadvantaged Credit: PA

When I put this point to Mr Swinney when I interviewed him he was adamant that if he had used these powers those at the bottom would have been hit disproportionately.

It is worth pointing out here that Labour's Jackie Baillie, when I pressed her on this, said her party would not put up the tax, and cited the same reasoning as Mr Swinney.

There is, of course, another reason the SNP did not want to put up tax for everyone in Scotland. There's a Holyrood election coming up in May.

However, Scotland is about to get even greater powers on tax, when Holyrood will be able to vary the rates and tax bands with complete flexibility.

There is a hint from Mr Swinney that might mean those at the top paying more and Labour appear committed to that too. Both say they will lay out their plans in advance of May.

Deputy First Minister John Swinney addresses the SNP National conference at Aberdeen Credit: PA

The Tories, on the other hand, are promising to be a tax cutting party, though we do not yet know the precise details of their plans.

Which may explain why Mr Mundell and his colleagues have a spring in their step.

It took some of them a long, long time to get to the point where they accepted it was a good idea to give Holyrood substantial new powers, including on tax.

Not those tax powers have arrived, with more coming, the Tories believe it forces their opponents - the SNP Scottish government in power in particular - into making choices on how to raise money.

In turn those choices have to be justified to voters.

Will it make a difference in terms of the outcome in May, which polls suggest will result in another huge victory for the SNP and Ms Sturgeon? Well, no sign of voter opinion shifting so far.

One thing is for sure, though, as one senior MSP put it to me here at Holyrood: "Scottish politics just got a whole lot more serious."