Colne Valley demonstrates the problem with three-way marginals: no-one knows who's going to win.
This semi-rural seat on the western side of the Pennines could be taken by any one of Britain's mainstream parties. In the 2005 election Labour's Kali Mountford's majority shrunk to just 1,500 votes - 1,501, if you want to quibble. Boundary changes have helped Labour ever so slightly, but with Mountford stepping down Labour don't have the incumbency factor to rely on. This is the kind of majority which David Cameron must take if he is to make any sort of progress at all. "We have to take that one, otherwise we're in trouble," as a Yorkshire Tory elsewhere in the county puts it.
Labour's new candidate, Debbie Abrahams, does not deliver the usual confident prediction of a sweeping victory when asked if she thinks she's going to win. "I'm optimistic, put it that way," she says in an interview at her campaign headquarters. Her caution would serve as a lesson in modesty to many other candidates' brazenly unrealistic forecasts. She knows this will be a close call.
Abrahams' Conservative challenger is Jason McCartney, a former RAF officer and sports journalist. He is standing in his first election - and says he, too, couldn't possibly predict the result because of this. "I keep saying to my team 'how are we doing?'" he says as he leaflets in the seat's leafy suburb ward on the outskirts of Huddersfield. "My campaign manager has fought every election here since 1987 - he says it's the best he's known it." As those included two victories, when Graham Riddick took and then held the seat in 1987 and 1992, things are looking up. But even the Tories' confidence has not quite reached certainty.
Part of the reason for that is the Liberal Democrat factor, a legacy of the traditional Liberal support here dating from Richard Wainwright's time. In 2005 the Lib Dems took 24%, compared to Labour's 36% and the Conservatives' 33%. Following Nick Clegg's strong showing in the TV debates, can candidate Nicola Turner leapfrog McCartney into first place? "When I walk down the street everybody knows who I am," Turner says excitedly. "Voters run out of their houses and shake their hands. You can take from that what you want!" In the 2010 campaign, it seems, anything's possible.
It's difficult to tell where Colne Valley begins and ends. The rolling valleys of West Yorkshire and this seat's six wards seem to blend into each other; much of the constituency is countryside, but its small towns and villages retain very similar feels. Even the leafy suburb of Lib-Dem held Lindley ward doesn't feel far from wide open green spaces.
The result is a seat where small differences in the character of each ward make the difference when it comes to councillors. Crosland Moor and Netherton, where Labour have two of the three councillors, features working class communities with a strong immigrant presence. This is traditional territory for the national governing party, but its hold at local government level has dwindled elsewhere. The Holm Valley wards, north and south, are five Conservative and one lib Dem - Last of the Summer Wine's roots here paint exactly the right kind of picture. In Golcar and Colne Valley ward, the middle classes have taken over old industrial villages like Slaithwaite and Linthwaite.
The Lib Dems hold half of the constituency's 18 councillors. But the Tories have a positive story to tell, too. Since McCartney's selection in March 2007 - "an absolute lifetime ago" - the Conservatives took 2,000 votes off the Lib Dems in the 2008 elections before topping the poll in the European elections "for the first time in living memory". Labour campaigners brush aside these results. "We've had some boundary changes which are in our favour," Abrahams says. "Certainly in terms of the results on the doorstep we've proving our vote is holding."
Accompanying Abrahams on the doorstep to test that claim, politics.co.uk found a mixed picture. Most of the residents of the Slaithwaite council housing were out, but those that were out appeared tentative. Some expressed support, but others wavered. The biggest vote-loser, without a doubt, was immigration.
It's not the economy, stupid
It's a problem for the mainstream parties across the north, as they struggle to confront the gap in perception between many of those on the doorstep and the level of debate at Westminster. Abrahams does her best to outline the steps the Labour government has taken, mirroring the explanations of Gordon Brown about the "tough but fair" points-based system. "It's too bloody late, isn't it?" one voter responded impatiently. Many of those in what should have been a traditional Labour heartland have simply lost confidence. They feel the steps taken to manage future immigration have come far too late. They're fed up.
Abrahams understands this - and acknowledges it can't be directly combated. So she's worked on projects targeting young people with a "positive message" about jobs. And she's organised a creative arts project bringing together colleges, businesses and advisors, "so people could see what was out there and not feel left behind". Abrahams realises this can't be solved within the short space of a campaign, however. "It's long-term stuff - not things you can do one week before the general election."
Immigration can provoke some funny attitudes from candidates, especially Conservative ones. The party's cap on future immigration fits in much more easily with the mainstream attitude witnessed on the doorstep in Colne Valley, but the candidate refuses to pander to views he finds unacceptable. McCartney says he talks about the positive benefits - that "there are a lot of Brits overseas as well" - and adds everyone agrees the Gurkhas deserve to come and live here. "If people still have extreme views - there was a lady I... [met] on the doorstep two months ago she was just too extreme. I said 'madam, your views are abhorrent, good evening'."
The Lib Dems' approach is very different. Unlike the Lib Dem candidate on the other side of the Pennines in Oldham East and Saddleworth, Turner backs her party's policy of an amnesty on illegal immigrants to the hilt. "We are saying, bring your names forward. If you've lived here a long time, if you've learned the lingo, pay your taxes and you can stay." This is unlikely to win her many votes.
If immigration is what the voters want to talk about, the economy is top of the candidates' list. It's what matters most in the next five years here, in any case: Colne Valley's three hospitals make the public sector a huge employer. Abrahams says voters remember the last recession - the "divided society", as she puts it. "Especially in the north, people won't forget that." McCartney comes up with comparably predictable fare. It will not come as news to small businesses that the Tory candidate thinks red tape should be cut. Nor is it a surprise he opposes Labour's national insurance rise. "Our position is you've got to tackle the deficit but also stimulate small businesses," he says.
Turner's approach is the most locally-focused. When asked about the economy she doesn't talk about the deficit or the dangers of cuts. She's interested in "one-man, two-van" small businesses which need support. The Lib Dems have been running a group offering them advice. Getting high-speed broadband is judged to be a priority.
It reflects her wider approach to the seat. She is the most local of the candidates and is even standing in Colne Valley ward for the council. Labour and the Tories say this shows she secretly expects to lose. Turner disagrees, of course. "What I've discovered as I've done that is some stuff you can solve in the council chamber. A lot of stuff you can't... What I want to be able to do is still keep my feet firmly on the ground, rooted in the community."
Turner and her aides view McCartney as the main threat. The Lib Dems, who are offering a very local candidate, are determinedly attacking his credentials as a 'local' man. They say he comes from Leeds; he was a candidate for the Lib Dems in Pudsey five years ago; and although his parents have lived in Colne Valley for 25 years, he has not spent much of his time there.
"My family are very much involved in the community through male voice choir, through golf, my mum knows everyone who knows bridge," he responds. "So I'm well-established in the area. A lot of people know me. And they know that when I talk about getting things done for the area, it's my family and friends that are going to be affected as well."
As for his initial political affiliation with the Lib Dems, McCartney says he was attracted to the party only because of their opposition to the 2003 invasion of Iraq. "I don't want to say anything bad against them now," he says charitably. But a "positive attraction to David Cameron's Conservative party" won him over.
It doesn't take long, as I accompany him stuffing leaflets through letterboxes, for his frustration to come through. McCartney says the Lib Dems are fighting a negative campaign. "They are obsessed with where people live," he adds. Ex-Liberal MP Wainwright never lived in the seat, he says, pointing out their "rank hypocrisy". And he says Vince Cable "stood for three different parties in six different constituencies". "It's backfiring for them," he says. "People are leaving the Liberal Democrats."
Is this likely to come down to personalities? Close races usually do. But the winner in Colne Valley could rest more on the organisational abilities of the campaign staff.
McCartney's get out the vote campaign is already underway; he excitedly tells me his staff are now focusing exclusively on those who have already pledged to support him. This is not rocket science, of course, and the other parties have similar plans in place.
"I think it's going to be close," McCartney says. "The votes are hardening up." Which campaign proves the most effective at getting the logistics right may be decisive in this thoroughly unpredictable seat.