Hunch. Polls on 8 October put the People's Party near 33% and Vox near 18%, together about half the vote.
The seats market resolves on the Interior Ministry provisional results at 100% counted and then the official summary in the BOE: YES if the People's Party with its regional lists, Vox, Cs, UPN and other parties to its right together win fewer than 176 of 350 seats in Congress. Politico Europe and The Guardian are the backup.
We looked for cases where a Spanish prime minister called a general election at least a month before the four years were up. We found nine since 1977, and seven with full seat results on official pages. Right-wing parties together won 176 of 350 seats only once, in 2011.