In a comment you mentioned that you're looking for a .csl citation style file, e.g. for use with Mendeley. It turns out that Mendeley has a generator for, and repository of such files. In particular, one can opt to search by example. Using that tool for citations of the form "(Campbell, 2007)" reveals some examples, the most relevant of which is a modified Chicago style that appears to be associated with Colorado State University - School of Biomedical Engineering:
(Ahlquist, 2009; Borges, 1999; Campbell, 2007; Mares, 2001)
Ahlquist, J. S., & Breunig, C. (2009). Country clustering in comparative political economy (MPIfG Discussion Paper No. 09–5) (p. 32). Cologne: Max-Planck Institute for the Study of Societies. Retrieved from www.mpifg.de/pu/mpifg_dp/dp09-5.pdf
Borges, J. L. (1999). Selected non-fictions. (E. Weinberger, Ed., E. Allen, S. J. Levine, & E. Weinberger, Trans.). New York: Viking.
Campbell, J. L., & Pedersen, O. K. (2007). “The varieties of capitalism and hybrid success.” Comparative Political Studies, 40(3), 307–332. https://doi.org/10.1177/0010414006286542
“CSL search by example.” (n.d.). Retrieved December 15, 2012, from http://editor.citationstyles.org/searchByExample/
Mares, I. (2001). “Firms and the welfare state: When, why, and how does social policy matter to employers?” In P. A. Hall & D. Soskice (Eds.), Varieties of capitalism. The institutional foundations of comparative advantage (pp. 184–213). New York: Oxford University Press.
I have not tried it myself, but I hope it does the trick.