The Alliance Party was formed in 1970 as an alternative to
sectarian politics. Alderdice was on the executive committee of the party between 1984 and 1998, chair of the policy committee between 1985 and 1987 and the party vice-chair in 1987, before becoming the party leader after the
1987 general election. He contested
Belfast East for the party in 1987 and 1992. the highest percentage achieved by Alliance in an individual seat in a
Westminster election until
Naomi Long's historic victory for the party in Belfast East in the 2010 general election. In 1988, in Alliance's keynote post-
Anglo Irish Agreement document, "Governing with Consent", Alderdice called for a devolved power-sharing government based on a voluntary coalition elected by a qualified majority vote. Throughout the late 1980s and early 1990s, Alliance's vote across Northern Ireland stabilised at between 6% and 8%. He was elected to the Northern Ireland Assembly for Belfast East in 1998 and became the assembly's first speaker, serving until 2004.
Mo Mowlam said that Alderdice's "political and parliamentary experience mean that he is well suited to carry out this role". Alderdice was a member of
Belfast City Council from 1989 until 1997 representing the
Victoria constituency. == Elevation to peerage ==