Several years later, in 88 BC, a Roman army was sent to put down an emerging Asian power, king Mithridates of Pontus. The army, however, was defeated. One of Marius' old quaestors, Lucius Cornelius Sulla, had been elected consul for the year, and was ordered by the senate to assume command of the war against Mithridates. Marius, a member of the "populares" party, had a tribune revoke Sulla's command of the war against Mithridates. Sulla, a member of the aristocratic ("optimates") party, brought his army back to Italy and marched on Rome. Sulla was so angry at Marius' tribune that he passed a law intended to permanently weaken the tribunate. He then returned to his war against Mithridates. With Sulla gone, the populares under Marius and Lucius Cornelius Cinna soon took control of the city.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): Who had successfully passed a law whose sole purpose was to lessen the power of the tribunate?
Sulla