The emergence of the radical right party Vox in Spain has dramatically altered the political landscape in this country. This paper carries out an analysis of the political manifesto of this party with a double aim: analyzing whether their political proposals qualify as ‘illiberal’ and assessing the extent to which the Spanish Constitution can constrain the party. As it will be showed, a number of proposals by this party do qualify as ‘illiberal’ and, if implemented, might deteriorate democracy in Spain. However, those proposals are hardly compatible with any reasonable interpretation of the Spanish Constitution. Given that such Constitution is very rigid, such proposals are not politically viable. This will force the party to face a constitutional politics dilemma: either the party moderates so that its proposals fit the constitutional frame, or it radicalizes and rejects the Spanish Constitution as an insurmountable obstacle to the realization of its policy preferences.