AT the weekend, polling guru John Curtice suggested a referendum be held to ratify the outcome of the Smith process considering further powers for Holyrood.

The professor's idea will almost certainly not be realised. Commission sources were clear yesterday it was not part of their tightly-drawn remit. As for the political parties, it's hard to see much appetite for a public vote. There are, however, good reasons for seeking a separate mandate for whatever package of Holyrood powers emerges, above and beyond passing manifesto references in the run-up to May's General Election. Without it, as Mr Curtice argued, the next phase of devolution will be bedevilled by claims it did not go far enough.

Despite the difficulties of reaching agreement on significantly different sets of proposals, it is inconceivable the Smith process will deliver nothing. The price of failure would simply be too great for the parties that instigated the commission: Labour, the Conservatives and the Lib Dems. It's equally unthinkable the package will not meet the parties' famous (and carefully worded) vow to furnish Holyrood with "extensive new powers" while recognising Scotland's place in a UK that "exists to ensure opportunity and security for all by sharing our resources equitably".

But the real question is not whether the eventual agreement conforms to the letter of the vow, as it were, but how it fares in the court of public opinion. Badly, fears Mr Curtice, unless a referendum were held to focus minds on the tricky balancing acts involved in devolving powers and give the new settlement as much legitimacy as possible.

It is already clear, if it was ever in any doubt, that the SNP will simultaneously support and oppose the new package, voting in favour at Westminster and Holyrood while listing its many deficiencies. Expect betrayal, Alex Salmond has warned.

But if it looks like the Nationalists want to be inside the Smith tent and outside it at the same time, that's because they are. According to the commission's terms of reference, laid down by the UK Government, the process will be "informed" by the Government's recent command paper, which amounts to a summary of the three Westminster parties' competing proposals. There is a commitment to "assess and take into account" proposals from the SNP and Greens as well, but their demands for devo max will surely fall at the hurdle of maintaining the integrity of the UK.

So an intense political fight over the outcome of the Smith commission is guaranteed. Indeed, Greens leader Patrick Harvie has already questioned the authority of the process by criticising the fast-track timetable and insisting it is giving insufficent weight to contributions from the public and civic Scotland bodies.

Some of those bodies, especially groups in the charity sector represented by the Scottish Council for Voluntary Organisations, are already complaining the process amounts to a stitch-up by the UK parties. When the the five Holyrood parties get round Lord Smith's negotiating table for the first time tomorrow, the tricky business of reaching consensus might seem a doddle compared with the inevitable battles to come.