We present fresh evidence of the influence of ideology on the Spanish Constitutional Tribunal. Examining all nonunanimous votes over the period XX up to XX, we apply Item Response Theory to model the judges latent preferences together with case parameters. We use information on appointments, prevailing perceptions of partisan alignment on the Court and comparisons of model parameters and actual voting behaviour in salient cases to validate our model. Our findings are consistent with previous research. The progressive-conservative dimension accounts for 88 per cent of voting behaviour in nonunanimous decisions. As expected in the Spanish context, constitutional disputes pertaining to the allocation of authority between the Comunidades and the central government stand out as particularly polarizing. To facilitate future research into separation-of-power dynamics, we also chart temporal shifts in the position of the ideological median.