South Antrim has been a major unionist battleground for the past decade, switching between the UUP and DUP on three occasions.
The decision by Ulster Unionist leader Sir Reg Empey to contest the seat takes this year's hostilities to a whole new level.
His leadership will be under severe pressure if he does not produce a much-needed win for the Tory-UUP cause.
South Antrim used to be ultra-safe UUP territory?
That all changed in 2000 when the DUP's Willie McCrea claimed a shock by-election victory against Ulster Unionist David Burnside. That was a significant early indication that unionist opinion was shifting against David Trimble's Ulster Unionists.
Mr Burnside was the winner in the General Election the following year, but Mr McCrea then reclaimed the seat in 2005.
Who starts ahead?
Mr McCrea's majority in 2005 was just under 3,500. The gap between the DUP and UUP widened to more than 5,000 in the Assembly poll two years later.
But that was before Ian Paisley said yes to power-sharing with Sinn Fein.
One of the DUP's Assembly candidates in 2007 was Antrim councillor Mel Lucas. He switched to the TUV after the devolution deal and is contesting the seat on May 6 for Jim Allister's party.
The size of the TUV vote will be a factor?
It will, but there are others too. The Conservatives-UUP selection process was messy, with Sir Reg belatedly entering the field after Antrim Mayor Adrian Watson was rejected as a candidate.
Mr Watson has publicly backed his party leader's bid for the seat, so it remains to be seen whether the controversy will make any difference.
Sir Reg could benefit from tactical voting from Alliance and SDLP voters who would prefer him to Mr McCrea.
However, the UUP link to the Tory Party may deter some potential supporters from those quarters.
Alliance leader and South Antrim MLA David Ford is not standing in this election, and that may depress its vote.
Antrim Councillor Alan Lawther is Alliance's runner this time.
What about the nationalist side?
There is no realistic chance of a nationalist taking the seat, but both Sinn Fein and the SDLP will want to maintain their vote, with next year's Stormont poll in mind.
Sinn Fein's Mitchel McLaughlin had the highest personal tally in the last Assembly election, due to the long list of unionist candidates in the field. Mr McLaughlin is standing here again, while the SDLP's hopeful is party worker Michelle Byrne.
And the nominations are?
Michelle Byrne (SDLP)
Reg Empey (Conservatives and Unionists)
Alan Lawther (Alliance)
Mel Lucas (Traditional Unionist Voice)
William McCrea (DUP)
Mitchel McLaughlin (Sinn Fein)