sentences:  The party incorporated the majority of Mexicans through their mass organizations, but absent from the structure for ideological reasons were two important groups, private business interests and adherents of the Catholic Church.Those two came together in 1939 to form the National Action Party, which grew to be the major opposition party, winning the presidency in 2000.The most powerful labor union prior to the formation of the party was the Regional Confederation of Mexican Workers (CROM), headed by Luis N. Morones, an ally of Obregón and Calles.