[arugulum]

>that they need to rig their elections against themselves to get dissenting voices

I don't believe this is true. If you're talking about Non-Constituency Members of Parliament, they are consolation prizes given to best losers, and there are many things they cannot vote on. Moreover, the ruling party almost never lifts the party whip, i.e. members of the party CANNOT vote against the party line (without being kicked out of the party, which results in them being kicked out of parliament). In other words, since the ruling party already has a majority, any opposing votes literally do not matter.

If you aren't talking about the NCMP scheme, then I do not know what you're talking about, as the ruling party does institute policies that are beneficial for the incumbent party.