 A new legal framework was established in the Constitution of 1917, which reversed the principle, established under Díaz, that gave absolute property rights to individuals.Northern revolutionary generals Alvaro Obregón and Plutarco Elías Calles each served a four-year presidential term following the end of the military conflict in 1920.The assassination of president-elect Obregón in 1928 led to a crisis of presidential succession, solved by the creation of a political party in 1929 by Calles, now called the Institutional Revolutionary Party, which held presidential power continuously until 2000.