Every vote matters - and that is particularly true in Fermanagh/South Tyrone.
Last time the winning margin in the UK's most tightly-contested seat could be counted on one hand, Michelle Gildernew's majority in 2010 a mere four votes.
That has since been cut to one, after a court examined disputed ballot papers and found three were unaccounted for.
Most expect another close battle this time around in what is effectively a two-way tussle between Ms Gildernew and Tom Elliott. The seats pulls together the spectacular topography of the Lakeland county and the southern half of Co Tyrone.
Geographically, it is the largest of the UK's 650 constituencies, and has traditionally delivered some of the biggest stories. Held at one time by the Duke of Westminster and at another by an IRA hunger striker, it has flipped between Orange and Green over the last 65 years.
In 20 contests since the seat was created in 1950, nationalists/republicans have won 10 times and unionists have won 10. Like last time, unionists are grouping behind a single candidate, with the DUP giving Mr Elliott a clear run against Ms Gildernew.
Despite her slender majority, many see Ms Gildernew as favourite.
Bill White from pollsters LucidTalk says: "Fermanagh/South Tyrone could be close again, with perhaps Sinn Fein having the edge because they're the incumbent - always an advantage in Westminster elections.
"The key to winning here is not the election campaign itself, but each party getting out their vote on election day. Sinn Fein have shown themselves to be masters of this in the past."
Last time the single unionist candidate, Rodney Connor, polled 21,300 votes - almost 1,000 less than the 22,213 votes for unionist parties in the 2011 Assembly election.
Mr Elliott will aim to overcome the traditional hostility between the DUP and UUP in Fermanagh/South Tyrone but admits he faces "a hell of a fight".
"Every single last vote will count. But if we work together and we all are prepared to put the time and effort in, I am sure we will once again see the most westerly constituency in the UK given back its voice," he says.
Ms Gildernew concedes she faces a battle to retain her seat.
"We don't take anybody's vote for granted, but we hope that people will vote for all the right reasons for myself as MP for Fermanagh/South Tyrone," she says.
Privately acknowledged as an able and articulate operator by her rivals, Ms Gildernew claims unionists vote for her.
However, she must persuade floating voters that she can deliver effective representation given her party's policy of not taking its seats in Parliament. Some also note that her profile has dipped after being replaced, first as Agriculture Minister, then as MLA, as part of Sinn Fein's move to end double-jobbing.
What could be crucial this time is how strongly the SDLP polls, and how many of its traditional support base Sinn Fein can entice. In 2010 TV anchorman turned politician Fearghal McKinney took 3,574 votes.
This time the SDLP candidate John Coyle is not nearly as high profile. Even senior party figure Alex Attwood didn't seem to know he was standing during a recent radio interview. Also running are Hannah Su (Alliance) and Tanya Jones (Green).