After the death of Vytautas, his successors were elected by the Lithuanian nobles and their policy was now independent. The union, though, however weakened, still existed, because both countries needed the support of each other against foreign enemies. Only in 1440-1492, when Jogaila's younger son Kazimierz was the grand duke, the union was brought into full force again, since Kazimierz was elected both the duke of Lithuania and the king of Poland. After his death Lithuania seceded from Poland again and elected a new duke, Alexander. Only in 1501, when Poland also elected Alexander the king, both countries agreed to keep the union and to elect one ruler for both countries. This was when the union of 1386 finally became solid enough.
In spite of these attempts of secession, the Polish influence in Lithuania was getting stronger. The grand dukes were Polonized Catholics and as their power grew, the political structure became more centralized and the Catholics obtained certain privileges. This led to discontent among the Orthodox Lithuanians. Some of them seceded from Lithuania and joined Muscovy, others simply moved to Moscow. So, Moscow learned more about the internal affairs and problems of Lithuania and some times even started wars. This threat forced Lithuania to seek the Polish support even more actively.
Not only the aristocracy of Lithuania suffered from the new policy of the Catholic rulers. The political structure of the early Lithuanian-Russian duchy was copied after the structure of the Kievan Rus (see chapter 20). Now, it began to imitate the Polish order characterized by strict borders between estates, extremely wide rights of the aristocracy (szlachta) and self-governing cities (according to the Magdeburg rights). Szlachta was turning into the ruling class. They elected kings, owned the lands and had unlimited power over the peasantry. This system was advantageous for the nobility but not for the others. So the enmity between the omnipotent aristocrats and the rest of the population grew.