Caesar's debts were so enormous by 63 BC that he was in danger of prosecution by his debtors. In order to stave off potential disaster, Caesar made a bold political move, deciding to run for the position of Pontifex Maximus. The head priest of Rome was in a position of considerable power, with opportunity for income, and therefore some limited protection from his debts. The Pontifex was elected to a lifetime term and while technically not a political office, still provided considerable advantages in dealing with the Senate and legislation. On the morning of the election, Caesar reportedly told his mother Aurelia, "today you will see me either high priest or an exile", indicating the importance of the election to him. Through additional bribery, Caesar was successful, gaining more votes than all of his opponents combined.
Later in the same year of 63 BC he also ran for, and won, the office of urban Praetor. Before he could even take office, however, the Catiline Conspiracy erupted putting Caesar in direct conflict with the optimates once again. Lucius Sergius Catilina, a consul candidate for 63 and 62 BC, was accused of hatching a plot to overthrow the Republic through armed rebellion. Whether Calilina ever did anything of such extreme measures up to this point, or was simply pushed into it through threats of prosecution and execution is disputed. At any rate, however, the resulting ordeal was both a defining moment in the career of Cicero and yet one more indication of the Republic's impending collapse. In the elections held in late 63 BC, Catiline was defeated for the consular position and soon afterwards, anonymous letters showed up at the house of Crassus. The letters informed various Senators to leave the city to avoid the coming massacre against certain other government leaders. Crassus, despite likely connections which would later be deemed the conspirators, took the letters to the Consul Cicero, who took the conspiracy concept to the Senate.
Many in the Senate disbelieved the plot, some even thinking that Cicero made the whole thing up for his own political gain. Cicero's oratory eloquence convinced the Senate, however, that extreme steps were necessary to combat the plot. While the plot against the Senators may have been fictitious, protests outside the city were growing due to the failure of small farms in Etruria. In a recurring theme throughout Roman history, they couldn't compete with huge slave operated estates owned by aristocrats. Former Sullan army members were gathering arms and preparing for open rebellion that was reported to begin on October 27 of 63 BC. A Senatus Consultum Ultimatum was passed granting Cicero the authority to deal with the conspirators, and Catiline, among others, became the prime target. Catilina decided to flee Rome, but not before being implicated in another plot to assassinate Cicero. This plot failed of course, but Catiline escaped to join the rebellion in Etruria.
In Rome however, other conspirators attempting to get the support of the Gallic Allobroges were caught in the act. Several people were arrested and the Senate met to decide their fate. Cicero argued for the death penalty without trial and had most of the Senate convinced, but Caesar, as the Praetor elect was allowed to speak and had the Senate nearly convinced that trials, and or lighter sentences were in order. Marcus Porcius Cato, the ultra conservative leader of the optimate party, then swung the decision back in favor of the death penalty. The budding rivalry between Caesar and Cato was turning into outright enmity and Cicero would forever hold a grudge against Caesar for his opposition. The optimates attempted to implicate Caesar in the whole affair, because he had many connections with the growing rebellion in Etruria and because of his outspoken opposition to the death penalty. Caesar's close ties to Crassus, as he was the one to present the letters of conspiracy to Cicero in the first place, seem to have exonerated Caesar from any potential penalties. Cataline, now with the rebel forces in Etruria, was soon defeated and killed, and the entire conspiracy was over.
In the following year, Caesar began to serve his term as urban praetor. Now in another elite position of Roman government, he once again pushed his populares policies. He first asked for an account of the cost in restoring the capital in which he was opposed by the optimates. Unsuccessful in that attempt, the next order of business was strengthening his standing with Pompey, who was set to return to Rome from his eastern campaigns. Pompey's return was a significant concern of the optimates, as they feared a Sullan type march to Rome and dictatorship. They needed to present the city, and the surrounding countryside, as a stable environment not in need of Pompey to 'restore order'. Pompey's ally, Caecilius Metellus Nepos, however, took the matter to the Senate demanding that Pompey be allowed to land in Italy and do just that. Caesar supported Nepos and Pompey, but the motion was defeated once again by Cato. Nepos fled Rome to join Pompey, while Caesar was eventually removed from the Praetorship. He was restored however, when a mob in support of Caesar threatened violence in his support, and Caesar quelled it before anything happened.