[7][8][9] In 1840, in collaboration with two other seminary students, he began his political career by writing a petition to the king of Naples, Ferdinand II, demanding a constitution.

[10] In 1843, he moved to Naples to work as tutor to the children of the magistrate Benedetto Croce, his maternal uncle, and grandfather of the famous philosopher of the same name.

[11] After the newspaper's first issue, on 1 March 1848, within a short time it became a point of reference for the liberal middle class, and even found favour in more conservative and royalist circles.

During this period he also founded, with the help of Luigi Settembrini and Filippo Agresti, a secret society named the Grande Società dell'Unità Italiana,[12] the aim of which was the overthrow of the Bourbon dynasty.

Spaventa, accused of supporting General Guglielmo Pepe's resistance movement, was arrested on 19 March 1849 and held in the prison of San Francesco.

He returned in October to take up the post of Minister for Police in the provisional[18] government (from November 1860 to July 1861), dealing vigorously with the difficult situation in the city, at times with the help of Rodrigo Nolli, a landowner from the same region of Italy as Spaventa.

He was appointed Under-Secretary to the Ministry of the Interior in the governments of Luigi Carlo Farini and Marco Minghetti, becoming the principal architect of the State's policy on internal security.

The resulting withdrawal of support from Tuscan members of parliament led to the fall of the government in March 1876 and the demise of the Destra storica political alliance.

He also fought tenaciously for a rigorous separation of the political and administrative spheres of government, and argued against Agostino Depretis's trasformismo, in favour of a British-style two-party system.