In 1975 Thatcher defeated Heath in the Conservative Party leadership election and became Leader of the Opposition, as well as the first woman to lead a major political party in the United Kingdom.
Ring 1975, ida ngalahang Heath ring Pamilihan kapemimpinan Partai Konservatif manados Pamimpin Oposisi, anak istri kapertama sané mimpin partai politik ageng ring Britania Raya.