Simplify the following text for a Grade 12 native English-speaking person.
Original: He returned to the House of Commons in October 1974 as the Ulster Unionist Party MP for the Northern Irish constituency of South Down until he was defeated in the 1987 General Election .
Simplified: In 1974 he left the Conservative Party , before the February election , and became an MP in Northern Ireland for the Ulster Unionist Party in October 1974 .