Candidates campaigning for seats in the most powerful Scottish Parliament ever will have bagfuls of extra goodies to offer this session but many people only have one question: "What's your opinion on Scottish independence?"

A Survation poll indicated half of voters will definitely not vote for a party which disagrees with their position on independence.

No matter how many tax breaks or benefits are on the table, the clinching policy will be how they leaned in 2014.

Scots have already been debating the problems MSPs will face in the next parliament - taxes, benefits, oil, health and education - but for some there are just two solutions: unionism or nationalism.

Now that Yes Scotland and Better Together have shattered into their constituent parts, Scots are faced with competing manifestos containing complex calculations over the right mix of tax-and-spend.

Rather than decide how much tax they want to pay and what services they will sacrifice to pay for others, half of Scots are happy to take what they are given as long as the constitutional question is correct.

Christine O'Neill, a specialist in constitutional law and chairman of Brodies solicitors, says constitutional arguments have become a "proxy" for other political questions.

"Clearly, people became incredibly engaged during the referendum process, with the turnout the most obvious sign of that," she said.

"The question whether to vote Yes or No became, to a great extent, a proxy for hopes and aspirations and arguments about other policy issues.

"Yes or No came to be seen in many quarters as a vote for the NHS, or for more spending on social care, or a vote on the future of education, or for or against Trident.

"I think that many of the new powers that have been transferred to the Scottish Parliament as a result of both the Scotland Act 2012 and the Smith Commission proposals are much less accessible or intelligible to the average voter.

"The fiscal framework remains obscure to most of us: what it means and how it will operate in practice.

"Indeed, I suspect many voters will not have heard of it. It is not a concept that lends itself to being an 'easy sell' by politicians on doorsteps."

If independence remains the catch-all answer for nearly half of Scots the next question for them will be: "When can we do it again?"

Nicola Sturgeon says she is ready to present "realistic and relevant" arguments to win indy-sceptics round in the summer but it is debatable whether she has the power to promise another referendum.

Holyrood does not have a straightforward mechanism to stage a legally-binding referendum but nationalists have a fall-back option of a "consultative referendum" if Westminster does not strike another Edinburgh Agreement.

Ms O'Neill, a former adviser to Holyrood's Devolution Committee, said: "The question is not, in legal terms, whether the Scottish Parliament can pass legislation to provide for a referendum. Rather, the question is about the legal risks of doing so.

"The Parliament could, in theory, pass a Referendum Bill at any time, even if the Presiding Officer thinks that such a Bill is not within the legislative competence of the Parliament.

"If there is a question about the legality of the Bill, it is then open to the Attorney General in England, the Advocate General and the Lord Advocate in Scotland to invite the Supreme Court to rule on whether the Bill is lawful before it receives Royal Assent.

"A reference of this sort has never been made in relation to a Scottish Bill, although it has been done with Welsh legislation, and to make a reference would be politically very controversial.

"So, what is more likely is that, in the absence of a fresh agreement to mirror the Edinburgh Agreement, such a Bill might receive Royal Assent but is then challenged in the Court of Session by one or more individuals who do not want to see another referendum.

"That kind of challenge could, of course, happen.

"The crowdfunding approach that was taken to the challenge to Alistair Carmichael's election demonstrates the possibilities.

"It seems inevitable, given the strength of feeling over the independence question, that funding for a challenge could be found."