Election profile: Ulster Unionist Party
The Ulster Unionist Party draws its support from the unionist community, the vast majority of whom are Protestant.
It was founded in 1905 when the Ulster Unionist Council was formed.
In 1921, Ulster Unionists formed the government of Northern Ireland after the island of Ireland was partitioned, and they held power until 1972.
That year, the Stormont parliament was brought to an end by Westminster and direct rule from London was introduced.
That took place amid widespread civil disturbances and attacks by the IRA during the Troubles.
The UUP was closely aligned with the Conservative Party but the relationship soured when the Troubles began in the last 1960s.
The party played a key role in negotiating the Good Friday Agreement in 1998.
In 2003, the Democratic Unionist Party overtook the UUP as the largest party in Northern Ireland at the Northern Ireland Assembly elections.
At its height the UUP had ten MPs, but its decline began in 2001 when it lost three Westminster seats to the DUP.
The then UUP leader, David Trimble, struggled to maintain his authority within the party, which was divided over its pro-Good Friday Agreement stance.
The party's Westminster representation dropped further when Lagan Valley MP Jeffrey Donaldson defected to the DUP following the party's poor performance at the Stormont election.
In March 2005, the Orange Order ended its 100-year formal association with the party, reflecting changes in both the religious organisation and in wider unionism.
After losing his Upper Bann Westminster seat in 2005, Mr Trimble resigned as party leader.
He was succeeded by Sir Reg Empey who, during his five-year tenure, oversaw further electoral losses for the party.
In 2010, the UUP and David Cameron's Conservatives agreed to field joint candidates, but none were elected.
Meanwhile, the UUP's last remaining MP resigned from the party in protest at the deal.
Lady Sylvia Hermon retained her North Down seat as an independent and the UUP lost its last foothold in Westminster.
Under Tom Elliott's leadership from 2010 to 2012 the party lost a further two MLAs at Stormont. Mike Nesbitt became leader in 2012 and, since then, three MLAs have left the party.
The party is keen to get a candidate re-elected to Westminster and in March 2015 it agreed a pact in four seats with the DUP, in the hope of regaining a seat.