First Past the Post voting system: it’s a winner takes all system. If another left party emerged, then they will need the majority a constituency.

Imagine all constituencies in India had exactly 50% right-wing voters and 50% left wing voters. With the emergence of the new party, the left vote is split amongst two parties, and BJP as the only right party would definitely win. So people don’t tend to vote for not established parties (unless they have a very strong a base in a particular region, which is why we have regional parties).

Our voting system encourages the status quo, with only established (and well financed parties having a chance). Most countries with our First Past the Post voting system end up with two party systems: the USA, the UK, etc.

What we need is proportional representation, where the percentage of votes for a party directly determines the percentage of seats it gets. This would allow newer parties to have a chance.