Miguel's claim to the Portuguese throne, often dubbed 'The Phantom Throne,' was rooted in a complex web of dynastic disputes and 19th-century political upheaval. His supporters, primarily legitimists and traditionalists, argued for his right based on the argument that his elder brother, Pedro I of Brazil (and IV of Portugal), had effectively renounced his claim to the Portuguese crown upon ascending the Brazilian throne. This perspective held that Pedro's subsequent abdication of the Portuguese throne in favor of his daughter, Maria II, was illegitimate as he no longer possessed the right to bestow it. They emphasized Miguel's position as the next legitimate male heir according to traditional Portuguese succession laws, particularly those preceding the liberal reforms, asserting that his brief reign (1828-1834) was the true continuation of the monarchy, unjustly interrupted by foreign intervention and liberal revolution. The core of their argument hinged on a strict interpretation of primogeniture and an anti-liberal sentiment that viewed Maria II's reign as a capitulation to modern, revolutionary ideals.

Despite the fervent support from his faction, Miguel's claim ultimately never materialized into a lasting reign, primarily due to a confluence of military defeat, international opposition, and the enduring strength of the liberal cause. The decisive defeat in the Portuguese Civil War (1828-1834) at the hands of Pedro's forces, backed by foreign powers like Great Britain, was a fatal blow. The Concession of Évora Monte in 1834 forced Miguel into exile and effectively ended his claim as a viable political option. Furthermore, the European powers, largely embracing liberal ideologies post-Napoleonic Wars, generally recognized Maria II as the legitimate sovereign, viewing Miguel as a reactionary figure disrupting the established order. His legacy, therefore, remains that of a claimant whose traditionalist ideals clashed irrevocably with the prevailing winds of political change, leaving his 'throne' as a historical what-if rather than a realized sovereignty. The lack of sustained international recognition and military strength proved insurmountable for the 'phantom king'.

Delving into the intricacies of Brazil's succession laws is crucial for comprehending the dispute surrounding Miguel's legacy, moving beyond mere speculation. Unlike some common law systems, Brazilian inheritance law (governed primarily by the Civil Code) often features a strong emphasis on forced heirship. This means a significant portion of a deceased person's estate is reserved for specific heirs, such as direct descendants, ascendants, and spouses, regardless of a will's provisions. A testator can only freely dispose of the 'disposable' part of their estate, typically 50%. This legal framework introduces considerable complexity when considering challenges to a will or claims of undue influence, as the law itself provides inherent protections for certain family members. Therefore, understanding the legal 'what is' – the codified rules of inheritance – forms the bedrock for analyzing the 'what if' scenarios of Miguel's situation.

The contentious nature of Miguel's legacy likely stems from critical questions regarding the validity and interpretation of any existing testamentary documents, or perhaps even the absence thereof. Brazilian law sets stringent requirements for wills, including specific forms (public, private, or closed) and witness mandates. A will found to be defective in form or procured under duress or incapacity can be declared null and void, effectively reverting the estate to the default legal succession rules. Furthermore, the concept of 'collation' (colação) requires heirs who received lifetime gifts to declare them for equalization purposes during inheritance division, potentially impacting the final distribution. The disputes around Miguel's estate, therefore, aren't just about emotional grievances; they are deeply rooted in legal arguments concerning the proper application of these complex succession principles, determining who legally inherits and to what extent, far beyond mere conjecture.