And of this much there could hardly be a doubt, that the accession of the general of the army, which had just returned victorious from Spain and still stood compact and unbroken in Italy, to the party of opposition must have as its consequence the fall of the existing order of things.
Government and opposition were equally powerless; so soon as the latter no longer fought merely with the weapons of declamation, but had the sword of a victorious general ready to back its demands, the government would be in any case overcome, perhaps even without a struggle.
Coalition of the Military Chiefs and the Democracy Pompeius and the democrats thus found themselves urged into coalition.

Personal dislikings were probably not wanting on either side: it was not possible that the victorious general could love the street orators, nor could these hail with pleasure as their chief the executioner of Carbo and Brutus; but political necessity outweighed at least for the moment all moral scruples.
The democrats and Pompeius, however, were not the sole parties to the league.

Marcus Crassus was in a similar situation with Pompeius.

Although a Sullan like the latter, his politics were quite as in the case of Pompeius preeminently of a personal kind, and by no means those of the ruling oligarchy; and he too was now in Italy at the head of a large and victorious army, with which he had just suppressed the rising of the slaves.

He had to choose whether he would ally himself with the oligarchy against the coalition, or enter that coalition: he chose the latter, which was doubtless the safer course.