Traditionally Northern Ireland/Ulster party politics has been described in terms of the Big Four since the early 1980s thirty years ago: the Ulster Unionist Party (UUP), the Democratic Unionists (DUP), the Social Democratic and Labour Party (SDLP) and Sinn Fein. The first three had been active at least since the early 1970s; the UUP had been active since before World War I and had been the ruling party from 1922 to 1972 when London initiated direct rule.
The UUP traditionally represented the interests of the wealthy upper class in Northern Ireland: the landed gentry and the manufacturers. In 1969-71 they were suddenly challenged from two directions at once. First, by the Alliance Party in April 1970, which had started out a year before as a pressure group pushing for more liberal and inclusive policies that would take into account the interests of the nationalist population, and from Ian Paisley's Protestant Unionist Party, which was opposed to that very inclusiveness and wanted that traditional unionist rule but with a fundamentalist Evangelical fervor.
Alliance took off for its first four years expanding rapidly as it attracted new members by the innovation of its policies. It reached its peak at just under 15 percent of the vote in a local government election in 1977 when it came in ahead of the DUP. That was the last time that ever occurred. Then Alliance went into a thirty-year period of stagnation as its support slowly leaked away due to the increased sectarianism. The republican prisoners' hunger strike of 1981 led to Alliance losing most of its support west of the Bann River that divides the two heavily-unionist counties of the East from the more nationalist counties of the West of the province. Sinn Fein appeared as a political party in 1982 and had the SDLP under threat. Liberal Catholics in nationalist areas supported the SDLP against the threat from Sinn Fein leaving Alliance only with nationalist support in the unionist areas of the East.
The Anglo-Irish Agreement of November 15, 1985 produced a unionist backlash with the UUP supporting policies that were little different from those of the DUP. The UUP remained the dominant party until the attempt to implement the Good Friday Agreement from December 1999 to October 2002 cost it its soft support among unionists who became increasingly nervous about nationalist gains and the failure of the IRA to disarm as called for in the Agreement. When the IRA finally disarmed in September 2005 it was the DUP rather than the UUP that gained the credit among unionists. In the spring of 2007 the DUP suddenly adopted the policies of the UUP and entered into power alongside Sinn Fein. The UUP and the SDLP, which had been overtaken by Sinn Fein for the first time in local elections in 2001, remained in the Executive but not in the driver's seats.
Alliance suddenly experienced a renaissance in 2010 when it captured Peter Robinson's East Belfast seat after a sex scandal involving Peter's wife Iris had weakened the family brand among unionists. Alliance had lost a close election to Peter Robinson in that same seat in 1979 when Robinson was first elected. Then Alliance leader David Ford was appointed Justice Minister when the ministry was created after the powers were devolved from London. Alliance was the natural compromise choice between Sinn Fein and the DUP as its members (and voters partially) consider themselves to be neither nationalists nor unionists.
As independent journalist John Coulter explains in this article, the UUP is now trapped between the religious bigotry of traditional unionism, which is best represented by the DUP, and the liberal views of Alliance. If it comes out for non-discrimination against gays it will alienate its traditional unionist supporters and if it supports discrimination it will lose its more liberal open-minded supporters to Alliance. Either way it loses. Will it lose enough to drop out of the Big Four? Stay tuned.