'Switch' votes could prove decisive
In a seat decided by a single ballot paper in the last election, the two main rivals in Fermanagh and South Tyrone claim they are set to win crucial votes from each other's perceived support base this time around.
Sinn Fein's Michelle Gildernew insists some unionists will back her on May 7 while Ulster Unionist Tom Elliott says nationalists have told him they are behind his bid for victory.
The numbers voting against the traditional grain may be minimal in a constituency where 42,601 votes were shared between the top two five years ago, but in what was the UK's most tightly fought contest in 2010 they could ultimately be decisive.
Mr Elliott is one of four candidates across Northern Ireland who have been jointly agreed by the UUP and their rival Democratic Unionists in a bid to maximise pro-Union representation at Westminster.
Mrs Gildernew first won the seat she has held for 14 years by 53 votes in the 2001 election. But that narrow margin looked relatively comfortable compared to the last Westminster poll.
After a series of recounts, she emerged with a four-vote majority. But that was reduced to just one vote by a later review by the electoral courts.
The former Sinn Fein agriculture minister at Stormont believes it is too simplistic to assume that supporters of the Union will vote for a unionist candidate.
"We can't assume that everybody who votes for me would vote for a united Ireland," she said.
The Dungannon born mother-of-three says unionists have been voting for her for the last decade. But she claims the numbers will grow, in part due to opposition at the unionist pact.
"There's more now," she said.
"Some of them tell me (they are going to vote for her), some of them tell other people and they tell me.
"I have a friend who is very great with a young Orangeman in Fermanagh and he told my friend that 'my family didn't vote for Michelle but we know lots of people who did' - so that's the kind of thing you hear back.
"And they are not telling you what they want you to hear. I am savvy enough to know that.
"It gives me great hope for the future. Fermanagh and South Tyrone is going to still be talked about as one of the most divided and polarised communities, but it is not.
"People vote on the basis of thinking through what they need to do for the future of their families."
Other smaller unionist parties, such as the Traditional Unionist Voice (TUV), Ukip and the NI Conservatives, are also not running, effectively giving Mr Elliott a clearer run at unseating Mrs Gildernew.
The Sinn Fein politician defeated another agreed unionist candidate, Rodney Connor, in 2010.
However, the parallels are not exact. Mr Connor stood as an independent five years ago. Mr Elliott is standing under his own party banner, so it remains to be seen whether unionist supporters of other parties will be as prepared to back someone who, on the other days of the year, is a political opponent.
The Orangeman and former UUP leader insists voters will forgo inter-unionist rivalries to oust Mrs Gildernew. Moreover, he believes his support base spreads beyond the unionist spectrum.
"It's a massive constituency, it's very tight and I think we are going to get a big vote again overall, it will be a high percentage vote," he said.
"I do have to say over the last few days I have been out, I have had a number of people - a couple of them I know personally, some I don't know - saying a similar thing actually, which is quite interesting, they are saying they are normally SDLP voters but they are going to give me their vote this time.
"Some of them know me, some of them know what I am like to work with, and they have said we feel you could represent us well Tom.
"Some of the others who don't know me say 'I just couldn't bring myself to vote for Sinn Fein, but I am comfortable voting for you'."
Candidate for the nationalist SDLP, John Coyle, dismisses any suggestion his vote will be squeezed in what most commentators predict will only ever be a two-way fight.
The 29-year-old was born and lives in the Belleek area in west Fermanagh. It is around 70 miles from Mrs Gildernew's home town in Co Tyrone, demonstrating the vast scale of the constituency. Mr Elliott, a farmer as well as politician, lives roughly half-way between them in the Fermanagh town of Ballinamallard.
"Everybody has the right to go up for election," said Mr Coyle.
"Nobody has the right to say that it is their seat. A seat can be won by anybody. You have to be the best candidate overall and I believe I am the best candidate and it isn't a two horse race.
"I am in it until the count is on and until we find out who is elected. I would be positive and forward looking that it will be me elected."
In such a razor edge marginal, hard blows were always going to be traded.
Sinn Fein has sought to highlight past remarks made by Mr Elliott when he referred to some of its party supporters as "scum" and also that he would not attend gaelic sports or gay pride events.
In response Mr Elliott has that Mrs Gildernew once referred to the DUP MP Gregory Campbell as a b******ks.
He also rejected Sinn Fein's portrayal of him as a Tory-backed candidate, noting that when he led the UUP he broke an electoral link with the Conservatives.
He added: "Yes, I said I have no intention of going to a GAA match or a gay pride march but does Michelle Gildernew go to the war memorial or cenotaph for Remembrance Sunday? She doesn't. Do I make a major issue out of it? No I don't. The reality of it is some people go to GAA matches, some people don't.
"That doesn't mean I don't know people and are friends with people in the GAA - I am. I have represented them on various occasions at planning committees and meetings."
For her part, Mrs Gildernew rejects the main criticism levelled at her by rivals - that as an abstentionist MP she is not properly representing the interests of constituents in parliament.
"People know how hard I work," she said. "They know if I have an issue to raise I can raise it in Belfast or Dublin, I can raise it in London and I can raise it in Brussels. I stand on a record of hard work."
She claims those Northern Ireland MPs who do take their seats contribute very little at Westminster.
"I see no reason to be on those green benches taking decisions on behalf of people in England and Wales," she said.
"I need to be here, making decisions on the island of Ireland for the people of Ireland."
Mr Coyle, who balances work on the farm with his job as a local councillor, points to the emotive issue of fracking as one where Fermanagh's case needs to be made in Westminster.
"People are just sick of Sinn Fein's absenteeism," he said.
"There are vital issues affecting this constituency, like fracking. If they want to stop it, it's at Westminster where you stop it coming into the UK.
"It has to be stopped in Westminster. That's where our three (SDLP) MPs have voiced their concerns about fracking.
"That's why we need somebody there to make sure it does not come into this constituency and keeps our lovely environment and our agriculture and tourism sectors alive and well."
Mr Coyle had a bruising experience on a TV debate at the outset of the campaign and claimed abuse that followed on social media amounted to cyber bullying. But he says the experience, which made headlines away from the campaign, has actually helped him.
"It has raised my profile and given me the opportunity to tell people about my policies that I am standing in this election for and showing them exactly what I can do," he said.
"I have had so much support over the past number of weeks (in the wake of the online abuse) it's just been brilliant. I am moving forward and looking to the future and it will only make me a stronger politician in the long run."
Alliance candidate Hannah Su accepts victory is not a realistic goal in a constituency where the party struggles to establish a footing between orange and green.
"It is difficult and it is an upward struggle sometimes," she said.
But the newly-wed from Dungannon makes a comparison with her progress as a runner, insisting she is part of a slow process to build Alliance support west of the River Bann.
"I am hoping to build the name of the Alliance party and that, in the future, someone will get elected," she said.
"I am not going to win but for me if I get 1,000 votes I would be over the moon.
"I do a lot of running. When I first started running about 10 to 15 years ago I was doing 10 kms in about one hour. With slow, steady training now my time is about 46 minutes and I actually won my first race before Christmas. I believe in the Alliance Party and I will always stick with the Alliance Party but it's going to take time. So I do think it is quite similar with my running. I think in life if there is something you want, if you really want it and you work hard for it, you will get it."
The Green Party is standing in a Westminster election in Fermanagh and South Tyrone for the first time.
Candidate Tanya Jones believes the fracking issue, and the campaign against the extraction of shale gas in the constituency, has changed the well-worn political dynamic in the area.
A planned exploratory drill in Fermanagh was shelved last year but opponents are steeling themselves for other commercial bids to frack in the gas-rich area.
"It's a new issue and it's a new kind of politics as well," said Ms Jones.
"People realised it was necessary for them to actually work together on the ground to protect their communities and one thing that's very significant is it brought together people from traditionally divided communities who realised that issues of pollution, issues of threats to health, to the future of industries knew no sectarian boundaries and people's interests were the same and it was not only necessary but also positive and good for them to work together.
"So I think there has been a very significant change in the way people see politics and how they see one another through that."