That the SNP was installed last night by the bookmakers, the real experts, as 1-4 favourites to win the Glenrothes by-election speaks for itself and is a measure of just how much the map of Scottish politics is changing.

Until last year the Nationalists had never won much in Fife apart from the odd council ward and a few regional list seats for Holyrood. But all that changed last year, when they won enough council seats to put them in the driving seat of a ruling coalition on Fife Council and, to put the icing on their political cake, took the first-past-the-post constituency seat at Holyrood of Central Fife (the old constsituency name for Glenrothes) from Labour.

One of the prime reasons for this sudden Nationalist upsurge was that the SNP was now perceived as having become more left-wing than Labour.

More important, however, was that throughout Fife the SNP had put in place a superb vote-gathering machine that made Labour's look as if it had come out of the Ark.

Identifying their voter base, they had also concentrated for three years on converting the 'softer' elements of the Labour vote and the party got its reward last year. Fife, as with other parts of Scotland, had simply lost patience with the Labour-led administration at Holyrood and with its Labour-led council and wanted a change.The Nationalists took massive advantage of Labour's disorganisation.

Labour had been guilty of taking its core vote for granted and simply did not see the Nationalist juggernaut coming until it was too late.

With Labour at UK level facing more woes every day and a leaderless party in Scotland, without personality or apparently much purpose, things for Labour in Fife have only got worse. That the crisis-prone Gordon Brown, himself a proud Fifer, is in Downing Street has perhaps become more a source of embarrassment to ordinary Fifers than a proud boast.

The Nationalists, meanwhile, have gone from strength to strength with the Holyrood administration under the cunning Alex Salmond, putting populism first with such policies as a council tax freeze.

Now Labouur faces another crucial Scottish by-election, this time in what many Scots refers to as the 'Kingdom' of Fife, a tribute to the area's sense of history, identity and position on the east coast jutting into the North Sea. Glenrothes, previously called Central Fife, takes its name from the village which became a town in the rush to create post-war new towns.

But it covers several other towns, such as Leven, Methil and Markinch, a host of small villages and even part of Kirkcaldy, Mr Brown's home town.

Glenrothes borders on the Prime Minister's constituency of Kirkcaldy & Cowdenbeath and is about ten miles from his Fife home. It plays host to electronics and offshore supply companies but there are notable pockets of deprivation dotted around the constituency.

Some of the owner-occupied property in less salubrious and out-of the way towns in the consttituency attracts some of the lowest prices in Scotland although just outside in places such as St Andrews there are some of the valuable properties in the country.

Like many areas which knew better days, the constituency has a hard core of unemployed and economically inactive voters, in some areas well above the Scottish average. Local politicians say drug abuse and crime are on the rise.

Politically, the area has always been well to the Left to the point that the former West Fife constituency (abolished in 1974) elected a Communist MP (Willie Gallagher) from 1935 to 1950. Central Fife, the constituency which preceded the present one, was the political home of Willie Hamilton, the fiercely anti-Royalty Labour MP.

The reverses last year for Labour came hard on the heels of the party's loss to the Liberal Democrats in 2006 of Dunfermline and West Fife. The man who carried the can for that was Gordon Brown, blamed by many in the party for appearing to take over the campaign and for being behind the selection of a candidate who was simply not good enough.

That by-election loss was the first real political blow for Mr Brown in Scotland in years and it had come in an area which he and, it is fair to say, most observers, regarded as his political fiefdom. If the bookies are right, he is about to be hit by another massive blow in Fife. This time it could be another nail hammered into his prime ministerial coffin.

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