Following law school, Klinefeldt clerked for Robert W. Pratt of the United States District Court for the Southern District of Iowa and for Christopher Armstrong and Benjamin Kaplan of the Massachusetts Appeals Court. He then worked in Boston at LibbyHoopes P.C. before returning to Iowa to work as counsel to the Barack Obama 2008 presidential campaign and the Iowa Democratic Party. From 2006 to 2009, he was an associate at Ahlers &amp; Cooney, a firm in Des Moines. He was also a member of the American Constitution Society.