Final answer:
Catiline garnered support from disaffected wealthy elites, the populares seeking reforms, and a private bodyguard of young men indulging in luxurious and criminal activities.
Step-by-step explanation:
Catiline relied on support from three types of people in his quest for power in the Roman Republic. The first group consisted of disaffected wealthy elites like certain publicans who had benefited under Sulla's regime but were now seeking more influence. These elites were often either sidelined by political shifts or simply seeking to amplify their wealth and social standing. The second group was the populares, which included figures like Julius Caesar who sought support from Rome’s citizenry by promoting reforms and benefits that appealed to the masses, especially those disenchanted with the Senate's traditionalism.
The third and final group consisted of Catiline's private bodyguard, composed of young, dissolute men described as his personal friends, who dedicated their nights to feasts and were reported to be skilled in less savory activities such as wielding daggers and administering poisons. This group represented the desperate and unscrupulous underbelly of society ready to commit serious crimes for political ends. They were known for their extravagant lifestyles and were a stark contrast to the traditional martial virtues of Roman society.