Quote (Black XistenZ @ 6 Apr 2019 14:28)
how likely is a split/mismatch between popular vote share and percentage of seats in parliament?
for example, say PP win 23% of the popular vote, and PSOE win 27%, would it be possible for PP to end up with more seats despite the lower vote share?
equivalently, could podemos get more seats than ciudadanos with their current projected vote share?
PP has traditionally received more seats than what their popular vote should grant them. That's because their usually the strongest party in rural areas, where the constituencies are small (2-4 seats). So, something like a 3-4% lead for PSOE could in reality be a tie when it comes to the seat allocation.
However, the divide between the 3 anti-Sánchez parties could result in PSOE winning in those small constituencies, which would eliminate the advantage PP has traditionally had, and a 3-4% lead for PSOE could now not only hold when translated into seats, but also increase.
Regarding C's and UP, it's a different case, because they are both urban parties that compete for the same constituencies, so there isn't as much of a discrepancy between them. However, due to their weakness in rural areas, they will struggle to make it into small constituencies, which will likely result in both of these parties ending up with less seats than what they deserve based on popular vote. In theory, Podemos will have it worse than Ciudadanos (assuming they'll receive less votes over all) since they'd likely be left out of the 3-5 seat constituencies while C's could secure a seat... but part of that could be compensated by the 4 basque and navarran constituencies, where C's is despised due to their stance against the medieval economic privileges these 2 regions have.