Mention the "Brown bounce" to Peter Grant and a look of slight irritation comes over his face.

When the death of John MacDougall MP was announced in August, it seemed the SNP's candidate in the resulting Glenrothes by-election had only to turn up in order to take the seat from Labour.

Fresh from victory in Glasgow East, an SNP victory looked certain but life, as they say, has a habit of getting in the way.

As the economic crisis worsened around the world, Gordon Brown's popularity at home experienced an unexpected surge.

Since campaigning began in earnest, and in particular since Mr Brown visited the constituency last week, there has been all to play for.

Mr Grant, leader of Fife Council, admits the result is likely to go down to the wire. However, as well as insisting he and his party are still on course to win, the 48-year-old is keen to dismiss the aforementioned return to favour of Mr Brown.

"Sections of the media are saying that the Prime Minister acted decisively over the bank crisis but it was 10 days after the Irish, with a rescue package lifted straight from the Scandinavians," he explained.

"His package was not original and I don't think the people of Glenrothes believe he acted decisively. At the end of the day, the banks the taxpayers bailed out are still not lending and it's clear that things are going to get worse before they get better.

"The people of this constituency are aware of the global economy but they are more worried about their jobs, their household bills and how this crisis will hit them personally."

Although he has an east coast accent, Mr Grant was born in another Labour heartland - Coatbridge in Lanarkshire.

He studied physics at Glasgow University, where he met his wife Fiona, a GP and fellow SNP councillor, and where his political life began. He admitted party politics did not interest him as a student, although he was stridently anti-Thatcher and took part in CND rallies.

After training as a teacher, Mr Grant moved to Glenrothes in 1983, saying he joined the SNP in 1987 after realising "Scotland was a different country that needed a different government".

Alex Salmond and Nicola Sturgeon have been drafted in during the last fortnight of campaigning, but it is clear the work needed to turn around Mr MacDougall's majority of more than 10,000 has been ongoing for months, if not years. Mr Grant, a quietly spoken man, may not have the jovial common touch of his party leader, but what he does have is a unique insight into Glenrothes and its needs after 16 years on the council.

Over that time, he's seen the fortunes of his party transformed. In the 1987 General Election, the SNP came last and in previous elections candidates routinely lost their deposits.

The SNP now has the sitting MSP, Tricia Marwick, and runs Fife Council in coalition with the Liberal Democrats. "Coming this far has been a huge achievement," said Mr Grant. "It's taken years of hard work to get here, knocking on doors and talking to people.

"But we've also been very loyal to the people of this constituency, we've looked after them. We have real credibility in this community.

"People on the doorsteps are telling me that I'm doing a good job as leader of Fife Council and that the SNP is doing a good job in Holyrood."

Mr Grant has been attacked by his rivals for upping some care charges for the elderly and charging for personal alarms that were previously free. But he is quick to defend his actions, insisting such "tough decisions" mean 1000 more elderly people are getting core services.

He also says those who can afford to pay more should do so. "There's no doubt that Fife Council has extremely limited resources and in the past there has been a real unwillingness to take difficult decisions.

"We're only 18 months into this administration and we've still got a lot to do. But I think people see me as an honest politician and at least respect me for that, even if they don't agree with everything I do."

There's little doubt that despite being just a hair's breadth from overturning a sizeable majority, it is the SNP, and not Labour, who are currently feeling the pressure. Anything less than victory for the Nationalists would mean the end of the extended honeymoon Mr Salmond and his party have enjoyed, a blow to the momentum that's been building since May 2007.

Mr Grant said he is "extremely confident" he will win the by-election, but added: "I've always said it would be very, very close, but even if we take this constituency by one vote, that will be a massive, unprecedented achievement. An SNP win in Glenrothes would break new ground."