In 2002, the ANC pushed through constitutional amendments allowing elected representatives to change party and keep their seats. In South Africa's proportional representation system, voters vote for parties, not individuals. When a representative crosses the floor, the seat -- which belongs to the party, not the person -- is effectively stolen from the voters who elected that party.
The most dramatic abuse occurred during the 2003 floor-crossing window. Through defections from the UDM and other parties, the ANC gained seats that increased its representation to 275 seats in the National Assembly -- a two-thirds majority that voters had specifically denied the party in the 1999 elections. A two-thirds majority allows constitutional amendments without opposition support.
Even more egregiously, following defections of NNP (New National Party) and UDM Members of the Provincial Legislature, the ANC gained an outright majority in the Western Cape legislature. Western Cape voters had voted for a coalition government; floor-crossing gave the ANC what the ballot box had not.
The post-crossing composition of elected bodies no longer represented voter preferences. Representatives who crossed the floor to join the ANC were rewarded with positions and patronage. The legislation was effectively a mechanism to override the will of voters without going back to the polls.
The ANC rejected floor-crossing at its December 2007 Polokwane conference -- notably, after the mechanism had already served its purpose. The constitutional amendment abolishing floor-crossing was tabled in 2008 and assented by President Kgalema Motlanthe on 6 January 2009.
The floor-crossing episode reveals a pattern: the ANC uses constitutional mechanisms to entrench its power when they are useful, then abandons them when they are not. Between 2002 and 2007, floor-crossing served ANC interests. Once the Zuma faction took over at Polokwane and no longer needed the mechanism, it was discarded.