 As a compromise, many principalities united with neighbouring regions and adopted constitutional forms of government, with the monarch acting as a mere figurehead while administration was left in the hands of elected parliaments.The trend in the 19th and 20th centuries was the abolition of various forms of monarchy and the creation of republican governments led by popularly elected presidents.Several principalities where genealogical inheritance is replaced by succession in a religious office have existed in the Roman Catholic Church, in each case consisting of a feudal polity (often a former secular principality in the broad sense) held "ex officio" — the closest possible equivalent to hereditary succession — by a Prince of the church, styled more precisely according to his ecclesiastical rank, such as Prince-bishop, Prince-abbot or, especially as a form of crusader state, Grand Master.