3746
From the beginning of the 2nd century BC , power was contested between two groups of aristocrats : the optimates , representing the conservative part of the Senate , and the populares , which relied on the help of the plebs ( urban lower class ) to gain power .
 organization: Senate
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 organization: Senate