It's first past the post voting that discourages niche candidates / affiliations. When you only have a single non-transferable vote, it's wasted if you place it on a niche candidate that doesn't get enough votes. So you're more likely to cast your vote for one of the top two or three mainstream positions - or rather, what you think is mainstream, what you think everyone else is thinking, influenced by visibility from media spending etc.
If you have a proportional system, where you can more truly state your preferences yet have your vote count even if your first preference doesn't succeed, you end up with more diversity. Downsides include greater tendency for coalition governments and potentially less clear mandates for decisive governments.
If you have a proportional system, where you can more truly state your preferences yet have your vote count even if your first preference doesn't succeed, you end up with more diversity. Downsides include greater tendency for coalition governments and potentially less clear mandates for decisive governments.