Is it permissible for an elected independent candidate or elected representative of a political party to switch his party he is elected from to a more politically advantageous party at his own will ? Is it his right to do so after his election?

Is not a fresh re-election process necessary? Is change of political party not a betrayal of trust reposed by the electorate in a leader or party he represents in a democratic setup?

What is the practice in leading democracies of the world? Are these written into the Constitution e.g. in the Representation of Peoples' act?