  We investigate the effect of bias on the formation and dynamics of political
parties in the bounded confidence model. For weak bias, we quantify the change
in average opinion and potential dispersion and decrease in party size. For
nonlinear bias modeling self-incitement, we establish coherent drifting motion
of parties on a background of uniform opinion distribution for biases below a
critical threshold where parties dissolve. Technically, we use geometric
singular perturbation theory to derive drift speeds, we rely on a nonlocal
center manifold analysis to construct drifting parties near threshold, and we
implement numerical continuation in a forward-backward delay equation to
connect asymptotic regimes.
