"To tax or not to tax - that is the question. Is it nobler to allow Scots to keep more of the money they earn, or to ask them to pay a little extra for health, education and housing?''

It may not be as poetic as the famous soliloquy penned by Shakespeare in Hamlet but it does sum up what many see as the defining moment of the campaign for the Scottish Parliament so far, and a question the Scottish electorate will be asked to decide between now and 6 May.

Last week in his third Budget, Chancellor Gordon Brown revealed plans to cut the standard rate of income tax from 23p in the pound to 22p from next year.

No tax cut

Two days after Mr Brown's announcement the SNP decided to ask the people of Scotland to do without that penny cut. Party strategists say the money raised, around £230m a year, will be used specifically to improve services in health, education and housing.

Alex Salmond: Wants to show "clear tartan water"

Political opponents say it will be a direct tax rise, the SNP say people won't be any worse off than now - they just won't get the next tax cut due to come in April 2000.

But whichever argument you accept, the upshot is that people living in Scotland would be required to pay more tax than those living elsewhere in the UK.

It has been the spark that has set fire to the campaign and the SNP hope it will show some clear "tartan water"' between themselves and other political parties.

At this point, it's worth taking a moment or two to recap a few of the main facts and figures relating to Scotland's finances. In the future, as now, the vast majority of Scotland's budget will be determined by Westminster.

This year Scotland will receive just under £14bn from the Westminster Treasury, next year it will rise to £14.5bn and the year after that more than £15bn.

The tax varying powers to the Scottish Parliament are pretty limited, the ability to raise or lower the basic rate of income tax by 3p in the pound.

That said, the SNP estimate keeping the basic rate of income tax at 23p in the pound will raise an extra £700m over the next three years, a sizeable sum by anyone's standards.

No 'Essex man' north of the border

With the elections to the Scottish Parliament still more than 50 days away, it's far too early to say if the SNP's move is the defining moment in the campaign. But there's no doubt the nationalists' move has focused the minds of the political parties on the perceived priorities of the Scottish electorate.

The recent received wisdom has been that tax and spend policies do not win elections. The SNP strategy is to some extent to snatch the clothes, long since discarded by old Labour in Scotland, in the belief that Scots will like the cut of the cloth.

The party thinks voters north of the border still hold a left-wing notion that services are worth paying for. SNP strategists say the referendum in 1997 gave clear backing to the tax varying powers, and if they're there it makes sense to use them.

They also argue that the crucial 'swing' voters in Scotland who, decide elections, are not the same in Scotland as in England. They say there is no equivalent in Scotland of the ''Essex man''.

Gordon Brown: SNP plans could cost £5 a week

Labour believe the SNP has made a serious tactical error, which could be crucial in the weeks ahead before 6 May and polling day.

The chancellor lost no time in getting on radio and television to warn that the SNP moves would make many Scots £5 a week worse off.

The Conservatives, who like Labour have pledged not to use tax raising powers in the first term of the Scottish Parliament, have also sought to point up the differences it would bring between Scotland and England.

Tory spokesmen said it would be equivalent to placing a sign at the Scotland-England border warning all northward settlers that are going to pay more.

The proposal to forgo the tax cut has received a warmer welcome from the Scottish Liberal Democrats. The party has said, if necessary, it would increase taxation to fund improvements in education.

The SNP's move also removes another potential hurdle in the way of a Holyrood coalition.

Both parties are now committed to raising income tax and proportional representation: both also oppose university tuition fees.

But the Liberal Democrats insist a deal between the two parties to run Scotland is still impossible unless the SNP gives up its demand for a referendum on independence in the first term of a Scottish Parliament.

The SNP leader Alex Salmond made a point in his speech of repeating that a referendum remains a key priority for a party seeking an independent Scotland.

There's no doubt the SNP have produced the ''big idea'' of the campaign so far.

In all honesty no one knows if it will be a vote winner or loser.

In that well worn phrase of political commentary when we don't know the answer ''only time will tell''.