Kinder, D. R. 2006. "Politics and the Life Cycle," Science 312(June 30, 2006): 1905-1908.
This article suggests that political attitudes are largely deterministic; that they begin to be shaped even prior to birth, with genetic components. They are then shaped by significant formative experiences in late adolescence and early adulthood, and then remain somewhat stable, although they are shaped by subsequent life changes. The author then argues that political participation is strongly effected by period effects, that is, by effects common to all born at a particular time (usually strongly affective historical events).
My take: This literature review is a helpful starting place to gather up the threads of the state of the literature in the effect of age on political attitudes. But I think it overdetermines the effect, arguing too strongly and not taking into account alternative explanations in the way that primary research does.