The Turbulent Reign of Isabel II: Political Instability in Spain

Elizabeth II: (1833-1868)
During the minority of Isabel II (1833-1843), Maria Cristina acted as regent mother. This period triggered the problem of succession and the Carlist Civil War (1833-1839), which faced the liberal supporters of the absolutist Isabel II and the defenders of Carlos. The Carlists were defeated, leading to the introduction of a liberal politician in Spain.
In 1843, Isabel II came of age, and her reign was characterized by political instability due to the ongoing confrontations between factions. The main groups were the moderate to high bourgeoisie and sections of the middle classes, including progressive artisans, who attempted to implement their ideas by drafting a constitution tailored to their needs.
The moderately liberal decade (1844-1854) was governed by the moderate constitution of 1845.
The two Progressive periods (1854-1856) saw the drafting of a new constitution in 1856, which ultimately was not enacted.
The decline of the Elizabethan monarchy (1856-1868) witnessed a shift in power from the moderates to the liberal Union (center). This increase in opposition to the regime spurred the emergence of more liberal parties, including Democrats advocating for universal male suffrage and Republicans who sought to abolish the monarchy.
The Revolutionary Six Years (1868-1874)
In 1866, the Democrats, liberals, and centrist progressives signed the Ostend Pact, agreeing to overthrow the queen. The Constituent Cortes convened to decide the political regime through universal male suffrage.
The revolution triumphed in 1868, leading to the exile of the queen and the formation of a provisional government, which promulgated the Constitution of 1869, the most advanced of its time.
There were two significant periods during this time:

Democratic Monarchy (1871-1873)

King Amadeo I faced political opposition from Republicans and supporters of the Bourbons. Amadeo abdicated in 1873, leading to the proclamation of the First Republic.

The First Republic (1873-1874)

This republic aimed to be federal and decentralized, sharing power between the central state and fifteen federal states.
These ongoing problems ultimately encouraged the restoration of the Bourbon monarchy.