Marius returned from his Germanic campaign in triumph once again. First hailed as the 3rd founder of Rome (Romulus was first of course, followed by Marcus Furius Camillus of the 'conquest of Veii' fame), and savior of the city, his success would be short lived.
Elected to his 5th straight, and 6th overall Consulship in 100 BC, he was proven to be out of his element without a war to fight. With the Republic secure from outside threats such as Jugurtha and the Germanics, Marius' policies were no longer to be tolerated. Directly on the battlefield after the defeat of the Cimbri, Marius had already pushed the envelope too far in the eyes of the Roman senate.
To appease his army, and of course to secure political support through their loyalty, Marius made unauthorized grants of citizenship to the Italian allied soldiers fighting for him. He then further pushed the Senate by demanding colonization and settlement rights for his large body of veterans. This strategy, under normal circumstances, would've been shot down immediately, but in this age of political turmoil, anything was possible. Using a popular and outspoken Tribune, Saturninus, Marius pushed through these proposals and others like it through the use of the citizen assemblies, mob tactics and open street violence. Saturninus used Marius to climb the political ladder, while Marius used Saturninus to push through his popular agenda, ripping apart the status quo and tearing down the traditions of Roman politics.
Marius lost what little credibility he had as a politician, and his strong-arm tactics eventually led to the exile of his old enemy Metellus. With the situation spiraling out of control already, Saturninus continued to push the limits of Tribunal power. In 99 BC, Saturninus organized the assassination of a political rival and mob violence grew to an unprecedented level. With Saturninus effectively taking control of the streets, the Senate had little choice but to turn to the one man who could stop it, the one man who gave Saturninus the power in the first place. A senatus consultum ultimatum, the highest authority provided for in the Roman constitution beyond the dictatorship, was issued by the Senate giving Marius the authority to stop Saturninus. Marius then ordered his troops into the city to quell the violence and take control from his former political ally. Saturninus and his supporters sought refuge in the Senate House, but despite efforts to have him arrested peacefully, angry political opponents took matters into their own hands. Climbing onto the roof of the Senate house, they pelted Saturninus and his mob with roof tiles, killing the majority of them. The crisis was over, but at the cost of Marius' reputation and the effectiveness of Republican law.
Except for the settlement of Marius' veterans, the Senate then declared the laws of Saturninus illegal and removed them from practice. While its probable that they would've like to void the veteran settlement laws as well, Marius' veterans proved an intimidating force of their own that would not go unnoticed by rising men such as Sulla. Even Marius' nephew, Julius Caesar, born only the previous year in 100 BC, would be highly influenced by Marius' use of the army to achieve political ends. Caesar, however, not only had the popular will of the people on his side, but the finest line of patrician roots as well. For Marius, however, his political career was coming to a temporary end. The Senate recalled Metellus, despite objections by Marius, and he knew life in Rome was getting to be too dangerous for him to stay.
At the close of his consulship, when a former magistrate could become legally liable for actions taken during his term, Marius went into a form of self-imposed exile. Satisfying the anger of the Senate, he took a voluntary leave and went east. But while his reputation as a politician in Rome was crumbling, Marius the general was a different matter. While traveling he met with Rome's future enemy Mithridates VI. Simply through a single conversation and his military reputation, he apparently convinced Mithradates that any plans for actions against Roman territory would be a disaster for him. His reputation as a force of power increased substantially, even while the Senate reviled him. While Marius drifted into political obscurity however, it was not to be the last of him. Rebellion among the Italians would force Marius to return within a decade, just as one major opponent, Sulla, was growing in power.