Reading up on the Roman Republic (currently re-reading Adrian Goldsworthy's Life of a Colossus) I have always wondered what exactly was the source of Cicero's power (autocritas)?
He was a "novous homo", he had zero martial success, he had very limited wealth, yet he was a mover and shaker in a world dominated by people like Caesar, Pompey, Crassus, Cato. All these guys had either an illustrious family line (Caesar, Cato, Clodius etc), or they were acclaimed as the greatest generals of their time (Caesar, Pompey) or was wealthier than half the Senate put together (Crassus). Now I am leaving out a lot of other names, but they would all fulfill one of the other criteria above.
Cicero was a successful lawyer, a plebian, had relatively no wealth, yet made consul, yet was considered a power centre in Rome.
The question is, from what or whom did he draw his power?
For one, the word you are looking for is "auctoritas", like "authority".
For Cicero, this came from being the greatest orator of his day. In Republican Rome, an orator was a much more political position than a modern lawyer, and virtually every one of his cases had him arguing for or against the political elite of his day. So while he was arguing cases, these cases would end in governors sent into exile or Senators cleared of all charges. The courts were the lifeblood of the Roman state, and Cicero was the master of them. It also made him extremely popular to the wider population, as everyone likes a good show.
It is also worth noting that he became extremely wealthy, and while his family was from Arpinum, his father was a prominent citizen there and the town itself was fairly important. And as a side note, of the people you mentioned, Crassus, Pompey and Cato were all plebeian; it was an irrelevant distinction at this point in history.