The National Party Government was never as unified as popular memory often suggests. Within their ranks, a number of individuals and factions interpreted their party mandate in a variety of ways. The issue that propelled the then Minster of Minerals and Energy Affairs to the forefront of the National Party, particularly the leadership of the Transvaal National Party, the second most powerful position in the party, was the resignation of Dr Andries Treurnicht. Treurnicht, a  hardliner Afrikaner nationalist (also known as a 'verkrampte', loosely translated to mean conservative), found the idea of a tricameral parliament totally unacceptable. Treurnicht believed that race should be the means by which White domination was legitimated. Treurnicht also felt that Botha in proposing a 'sham consociationalism' government, that mimicked power sharing to the extent that White rule was unchallenged by maintaining white majority in Parliament, the ideological path that the National Party was following, had deviated far enough from the path set by Verwoerd.

The leader of the National Party at the time was P.W. Botha.  On  24 February 1982, after vigorous debate, a motion of full confidence was passed in Botha and his right to interpret Party policy. Treurnicht proposed that the constitutional amendments, inter alia, the tricameral parliament, as suggested by Botha be discussed and put to a vote in his stronghold of Transvaal. de Klerk and others saw through this political feint and unknown to Treurnicht, invited Botha to the Executive council meeting that Treurnicht had convened. This resulted in Treurnicht and his supporters losing the eventual vote. This was also the end of Treurnicht's leadership of the National Party in Transvaal.  On 6 March 1982, de Klerk was unanimously elected as leader of the Transvaal National Party. Thus positioned, De Klerk would eventually succeed Botha as leader of the National Party and of Apartheid South Africa.

References:

1. Welsh, D. (2009). The Rise and Fall of Apartheid. Johannesburg and Cape Town: Jonathan Ball Publishers.
2. F.W. De Klerk, [online], available at:  myafrica.allafrica.com [accessed 28 February 2010]
3. F.W. De Klerk [ online], available givengain.com [accessed 28 February 2010]