Cause:
Don Miguel, the head of the reactionary party, was betrothed to Donna Maria, daughter of Pedro of Brazil. In 1828, disregarding his professions of loyalty to the Constitution, he declared himself King of Portugal. The Constitutionalists, who were adherents of Donna Maria, were crushed. She received no assistance from outside to deal with the usurper.
In Spain Don Carlos, the King’s brother, was the representative of the reactionary party. King Ferdinand, before his death, issued the Pragmatic Sanction, which enabled his daughter to succeed to the throne. The King was weak and unpopular, and Don Carlos had a great following in Spain.