In general, the amount of influence a party has on a decision varies depending on the scope of conflict -- that is, the people involved in the decision. The classic example is environmental policy. When decisionmaking scope is limited, industry has more influence. Policymakers are influenced by lobbying efforts, effective persuasive use of science, and economic benefits. When scope broadens, the public at large and news media are not persuaded by these techniques and instead respond emotionally to imagery of loss of a pristine, idealized, unspoiled wilderness.
Each partisan group seeks to manage scope to serve their interests.
In general, scope contracts with time, because the public has a limited attention span. Those parties most directly affected by policy, however, are unwavering in their attention. This is postulated as one reason why gun control efforts in the U.S. have stalled in the last decade: gun owners always care passionately about gun control, while gun control advocates divide their attention among many issues. When faced with an unwanted scope expansion, affected parties will usually try to delay any decision in an effort to contain scope.
Scope expansion can occur slowly, through education and outreach programs. Less often, public outrage can result in a rapid expansion of scope. Public demonstrations and civil disobedience can perhaps best be understood as efforts to expand scope of conflict.
See ExpandScope, LimitScope