Torcuil Crichton hits the road and the miles on a journey to sense the mood of the country as a crucially important Holyrood election rolls around. This week he starts his journey in Gordon, the seat Alex Salmond has to win if he is to realise his dreams of power

Close your sun-soaked eyes and listen to a description of the Gordon constituency, with its rolling meadows, its industrial mixture of textiles, distilling, beef rearing and quality food processing and you are transported abroad. You imagine these market towns and the networks of family farms along winding country lanes are not in Scotland's northeast, but some pastoral region of Italy where the tomatoes ripen on the vine instead of under plastic.

Then blink again, and you're sharing a microwave lasagne with Nora Radcliffe MSP at a garden centre cafe in Inverurie and realise, hey ho, we're back on the campaign trail.

Reviewing my cycling notes of the 2003 election, Gordon was marked down as a place where silage bales were the tumbleweed of an unpopulated landscape. It was a place on the way to somewhere more exciting, like the outdoor swimming pool at Portsoy. The last election was so humdrum that cycling was an option: this time I'd need a Tardis to get round all the marginal seats.

But there are good arguments for not moving out of Gordon. This time the huge constituency, stretching from the coast north of Aberdeen to the banks of the Spey, will be the crucible of the Scottish election campaign.

The reason: Alex Salmond, leader of the SNP, needs a Holyrood seat and has decided to risk all and stand for the constituency. Salmond may be king of the Picts, but he faces a huge task just to become MSP for Gordon.

The SNP are in third place in Gordon behind the Tories and sitting LibDem Nora Radcliffe. Even with boundary changes taking in some of Salmond's Banff and Buchan Westminster seat, it will take a 7.75% swing to get Salmond elected, and the LibDems are not going to roll over that easily.

Gordon is the SNP's 19th most winnable seat. If they win here, the party is a hairsbreadth from power and Salmond will be first minister. If they don't win here well, if they don't win here, it's game over for Alex Salmond.

SNP gains in neighbouring constituencies might deny him a list seat. He could have gone for a safer seat, could have marched into Aberdeen Central like the Jacobite army into Edinburgh, virtually unopposed. He could have gone to Dundee, or tried to elbow his SNP replacement Stewart Stevenson out of the old berth in Banff and Buchan. Maybe he did try. When I ask why that didn't happen, Stewart Pratt, Salmond's election agent, gives me a tiger's smile.

"The simple reason is that he wants to be first minister," says Pratt in a rolling Doric dialect. "He's not taking an easy option when he's asking other candidates to go out there and win hard seats. An easy seat is not a serious option in this election. We're going to lead by example and win in Gordon."

Pratt has nursed Salmond in every election since 1987, and for two nights a week and every Saturday for a year he's spoken to more people in Gordon than he's ever done before. If the SNP get their support out they will win, he says. That's what you expect a campaign manager to say.

Salmond has a reputation as a gambler, but this is a leadership risk akin to Napoleon's march on Moscow. It's Gordon or bust.

"Then it's got to be Gordon," says Salmond in an ebullient phone call in response to my ships-in-the-night request. He is heading north to the seat just as I am heading south out of it.

"Everyone who stands in this election is putting themselves on the line and I'm no different," says Salmond. "But I've been in politics long enough to know that people don't make up their minds in the last few weeks."

Although the LibDems in Gordon are anticipating an SNP explosion on the ground in the next few weeks, they and the nationalists have been bashing phones and knocking doors for months across the constituency. Really it's a super-by-election campaign, with rival party workers poised to flood in as the vote approaches.

Salmond can't be everywhere at once, and leading a national campaign limits his local availability. Radcliffe, on the other hand, is chapping on the doors every day of the week, and she's offended nobody in her two terms as MSP. Charles Kennedy has committed himself to helping her twice a week, Nicol Stephen is dropping in and Simon Hughes will be here - sans yellow taxi - this week.

Salmond's national profile helps, but all politics in the end are local. He may be a divisive figure, but he runs a slick constituency operation. He owes all his political success to the people of the northeast, and prides himself on being, if not the best politician, then the best constituency politician in Scotland.

He loves telling the story of two wee towns, Old Meldrum and New Deer. Each faced the loss of its Clydesdale Bank, but in New Deer, in Salmond's Westminster constituency, he helped organise a community buy-out and a sale to the Royal Bank of Scotland. The rebranded bank remains at the thriving centre of the town. Some 12 miles south in Old Meldrum, in Gordon, the closed doors lend the place a derelict tinge.

Some disagree, but I think it's part of an politician's job to facilitate community campaigns like that," says Salmond. "People know and acknowledge these things." We've all seen and heard Salmond bluffing and huffing over the years, but this time he seems to be genuinely happy. "Remember, it's got to be enjoyable too," he says. "Fighting a marginal again, it fair gets the blood flowing."

The bucolic image of the constituency is changing quickly. Oil-soaked Aberdeen long ago created a huge and wealthy commuter belt out to rural Aberdeenshire. You see them, morning and evening, snaking their way in and out, one occupant per car, to Furryboots City. It's not all boom time - you can buy the Big Issue outside Boots in Inverurie, but at Thainstone mart on Friday morning the money changes hands in the blink of an eye.

The mart is the biggest indoor livestock auction in Europe, and the auctioneer rattles through lots at the speed of light. It's so quick, all nods and winks, that it's hard to tell who's buying what. Discerning the politics is just as difficult. Although the gamble on Gordon is going to be crucial, most people haven't focused on an election yet.

"I think Salmond will make it, because everyone's so fed up with the other lot," says Susan, a medical researcher who's come to auction an orphan lamb but forgot to tag it.

George Wordie, at the store cattle sales, violently disagrees. "That man, he's a recipe for disaster," says the octogenarian. "Anyone but him." Stephen Singer is more interested in the ewe prices, which are not good. "I'm so busy with the lambing that when I come in at night, the news might be on but I don't take it in. Not yet anyway."

It's the same message on the doors from Port Elphinstone to Ellon. Too early to tell, there's a long and hard campaign ahead. Head spinning from politics and auction prices, the music on the car radio reminds me what I really ought to do: head for Lonmay, whence Andrew Presley left Scotland in 1745 to settle in North Carolina. Nearly 200 years later, in January 1935, his direct descendant Elvis Aron Presley was born in Tupelo, Mississippi. The rest is rock'n'roll history, but you'd never know it from anything in Lonmay.

A boilersuited Denis McDonald looks up and down the row of council houses that make up most of the settlement. "Well, it isna' Memphis," he admits. The northeast is a bit like that: understated, reserved but maybe, just maybe, with the potential to change the world.

Change in Gordon depends on what Tory and Labour voters do. The Conservative candidate, Nanette Milne, admits her supporters have to make a choice between head and heart. They hold the key to the seat and could grant Salmond power to frustrate Gordon Brown or stop the independence bandwagon here. Or, as Milne would have it, hold fast and march through the middle to win.

An indication of the effort Labour is putting into Gordon comes from the fact that their candidate, Neil Cardwell, can be found campaigning in Aberdeen Central, which, apart from Dundee West, is Labour's last barbican in the region.

In the Labour offices, Lewis Macdonald MSP is changing socks before going back out to pound pavements. A former transport minister who pushed through the all-important funding for the city bypass, MacDonald doesn't expect thanks. He's fighting for political survival and knows the antenna has detected a shift to the SNP. Blair is still an albatross for Scottish Labour, but anger over Iraq, even on this day when four British soldiers and their translator have been killed in Basra, seems to have dissipated.

At the top of Union Street the war is playing big. Black Watch, the National Theatre of Scotland's gift to the nation, is playing Aberdeen. It's a raw, unsentimental soldiers' tale, a staggering performance punctuated by the thud of the mortars which, as one character states, we'll be hearing for years to come.

Black Watch is a once-in-a-generation piece of electrical, political theatre, but the real democratic powerplay is in the hands of the audience in the Harlaw Academy gym hall. Some will be voters in Aberdeen, others will come from the rural hinterland where the most crucial votes in Scotland will be cast.

As the performance begins the bagpipe music skirls, the saltire floodlights sweep across the floor and dance on the faces of the crowd. You can't tell just what they're thinking, but you know a huge drama is about to unfold.