The Spanish general election of 2015 under the same electoral model I employed to model the 2016 ones here.
The results are as follows:
Total Seats: 400 [350 OTL]
People's Party (centre-right): 120 seats [123 OTL]
Spanish Socialist Worker's Party (centre-left): 92 seats [90 OTL]
Podemos (left-wing populism): 87 seats [69 OTL]
Ciudadanos (liberal, centre): 58 seats [40 OTL]
Popular Unity (left-wing): 15 seats [2 OTL]
Republic Left of Catalonia (Catalan separatism, centre-left): 10 seats [9 OTL]
Democràcia i Llibertat (Catalan separatism, centre-right): 9 seats [8 OTL]
Basque Nationalist Party (Basque nationalism, centre-right): 6 seats [5 OTL]
EH Bildu (Basque separatism, far-left): 2 seats [2 OTL]
Canarian Coalition (Canarian regionalism, centre): 1 seat [1 OTL]
The main result derived from this more proportional allocation of seats is that the regionalist parties lose some power and that the left is generally strengthened. The sum of PSOE, Podemos and Popular Unity adds up to 194 seats out of the 201 required to invest a President of the Government. All it would take would be to add the seats of PNV and CC (generally considered parties that support whoever offers them the most money for their regions) and 201. I must note that this was not done on purpose, but it's the natural byproduct of a more proportional system. That being said, if Popular Unity had obtained 0.69 pp. less it would not have acquired any compensation seats (threshold: 3% of the vote), and only gotten the two constituency seats hence probably forcing a situation eerily similar to OTL's.
The results are as follows:
Total Seats: 400 [350 OTL]
People's Party (centre-right): 120 seats [123 OTL]
Spanish Socialist Worker's Party (centre-left): 92 seats [90 OTL]
Podemos (left-wing populism): 87 seats [69 OTL]
Ciudadanos (liberal, centre): 58 seats [40 OTL]
Popular Unity (left-wing): 15 seats [2 OTL]
Republic Left of Catalonia (Catalan separatism, centre-left): 10 seats [9 OTL]
Democràcia i Llibertat (Catalan separatism, centre-right): 9 seats [8 OTL]
Basque Nationalist Party (Basque nationalism, centre-right): 6 seats [5 OTL]
EH Bildu (Basque separatism, far-left): 2 seats [2 OTL]
Canarian Coalition (Canarian regionalism, centre): 1 seat [1 OTL]
The main result derived from this more proportional allocation of seats is that the regionalist parties lose some power and that the left is generally strengthened. The sum of PSOE, Podemos and Popular Unity adds up to 194 seats out of the 201 required to invest a President of the Government. All it would take would be to add the seats of PNV and CC (generally considered parties that support whoever offers them the most money for their regions) and 201. I must note that this was not done on purpose, but it's the natural byproduct of a more proportional system. That being said, if Popular Unity had obtained 0.69 pp. less it would not have acquired any compensation seats (threshold: 3% of the vote), and only gotten the two constituency seats hence probably forcing a situation eerily similar to OTL's.