For a democracy to function successfully voters need a selection of candidates to choose from.
Different voting systems give voters more or less choice over which candidates get elected. At the lowest level some non-democratic countries will often run ‘elections’ with just one candidate. In democratic countries, voter choice often means whether voters choose individual candidates, or simply vote for parties.
With ‘Closed List’ versions of Party List Proportional Representation, voters vote for a list of candidates chosen by their preferred party. With systems with one MP per constituency, like First Past the Post and the Alternative Vote, each party chooses just one candidate to stand. In both cases, voters who’d like a party to form the government, but dislike their local candidate have no way of expressing themselves.
‘Open List’ forms of Party List Proportional Representation and the Single Transferable Vote both allow voters to choose between candidates of the same party. This creates a high level of voter choice.