Constitutional structures and devices can affect party politics. In Northern Ireland, such matters helped to increase conflict in the late-1920s and the 1930s. New arrangements, as a result of the Belfast/Good Friday Agreement, have helped to create political accommodation and relative peace.
Recently, however, potentially damaging controversy has arisen over the positions of First and Deputy First Ministers and questions of Orange or Green unity due to a crucial change contained in the St Andrews Agreement.
In the 1920s, some leading politicians in Northern Ireland sought to prevent politics becoming totally polarised. Sir James Craig was an enthusiastic Orangeman. In mid-1921, however, he became Prime Minister of Northern Ireland, which changed matters. In 1922 it was Craig in Parliament who rejected a request to make July 12 a public holiday.
In subsequent years, the Twelfth did become a public holiday. For three years, Craig took no part in Twelfth parades. This non-attendance was clearly part of an effort to avoid close public connections between his position as head of the Government and his Orange membership.
On July 12, 1927, Craig returned again to the Field in Belfast. He came to announce the Government's plan to end proportional representation in Northern Ireland Parliamentary elections to curb independents.
At the General Election in 1921, the Unionist Party won 40 seats, but in 1925 they lost eight to independent unionists, Labour representatives and other independents, leaving a small unionist majority.
If the Unionist Party lost its majority it was feared this would end the Union. The Government now passed legislation to abolish PR (which had helped independents) and made elections into a straightforward fight between the unionist and nationalist parties.
Besides changing the rules, Craig and other leading unionists began to develop publicly the Orange-unionist link, to promote unionist unity. From the early-1930s onwards, elections in Northern Ireland became largely straightforward headcounts.
We know only too well the consequences of such political stalemate. Our situation today, however, is improved greatly.
The Belfast/Good Friday Agreement of 1998 has provided a widely-agreed set of arrangements based around the consent principle which allows protection and accommodation of key different national views of the unionist and nationalist communities. It also prevents polarisation by allowing for divisions within the main political groups and permitting other parties to play a part.
The 1998 agreement provides not only PR, but also a form of government Executive, based on the main unionist and nationalist communities in our society.
Each community, however, is represented by two parties which reflect significant differences of both background and current policies. On the one side, we have the SDLP and Sinn Fein and, on the other, the DUP and the UUP.
Such diversity of opinion, along with that of other non-Executive parties, is essential in order to prevent complete polarisation. Changes to the method of election of First and Deputy First Minister, introduced behind closed doors at St Andrews and not subject to referendum, unlike the 1998 agreement, now threaten this arrangement.
First and Deputy First Minister are equal in power and role in the Executive, but the post of First Minister has a special status.
Under the 1998 agreement, the post of First Minister went to the largest party of the largest community, which resulted in a unionist taking the position. Under the St Andrews Agreement the post goes to the leader of the largest party, which could be the DUP or Sinn Fein.
This change could have very damaging consequences for our political system. It has led to calls for Orange and Green unity to give support to the largest parties, the DUP or Sinn Fein, or some type of new grouping, which will cause the effective demise of the UUP and the SDLP.
At elections, this drive to polarise tribal positions will damage other parties such as Alliance, the Greens and the PUP. Such developments must be avoided. The DUP and Sinn Fein today are the leading partners in shared government, but they took this role only after delays and qualifications.
It is the other parties - in particular the SDLP and the UUP - which took the lead in creating the present conditions of accommodation and stability.
The future success of these latter parties is essential to ensure the maintenance of our new structures and to avoid the creation of a totally polarised society.
This device to elect the two top positions in the Executive, agreed at St Andrews behind closed doors, should be changed. It was not what people voted for in 1998.
The British and Irish Governments must restore the spirit of the Belfast/Good Friday Agreement. This can be done either by reverting to original arrangements or establishing joint First Ministers of equal status.