OED 3. A party in the state or in any community or association. Always with opprobrious sense, conveying the imputation of selfish or mischievous ends or turbulent or unscrupulous methods.
4a. ‘Party’ in the abstract; self-interested or turbulent party strife or intrigue; factious spirit or action; dissension. †to be in faction with : to be in league with.
James Madison, Federalist #10: "By a faction, I understand a number of citizens, whether amounting to a majority or a minority of the whole, who are united and actuated by some common impulse of passion, or of interest, adversed to the rights of other citizens, or to the permanent and aggregate interests of the community."