In principle, coalitions are held together by belief in a common cause. Membership is often flexible and responsive to coalition positions.
The strongest coalitions are unanimous in every vote; each member fully supportive of every position. Sometimes a member may stand in the way of the coalition’s desires; called a veto, which is fine once in a great while. Even the strongest coalitions compromise occasionally to hold the group together.
Yet when a member repeatedly blocks or disagrees with others, it’s probably time to adjust the membership of the coalition. Those that don’t agree, consistently, don’t belong.
Practical Tip: Go for “unanimous” on every decision. Publicly support, as a coalition, only those things that each of you support. Use vetoes very sparingly.
Let the edges of membership be defined by the members’ agreements with each other. If you generally agree on what the coalition has done and where it’s headed, stay or join. If you don’t generally agree, leave or don’t join.
Do not let just one or two disagreeable members hold up coalition action over and over again. It’s okay to kick someone out of a coalition because they consistently don’t agree with what everyone else wants to do. And it’s okay to invite new members who are consistently supportive.