Final answer:
This response examines a policy from the 109th Congress that has been minimally successful due to the influence of interest groups and decreasing legislative productivity.
Step-by-step explanation:
The question asks for an identification and analysis of a policy enacted by the 109th Congress that has been used for several years with limited success. The variables that may be inhibiting success include the influence of interest groups, which often find ways around such limitations. One example of a policy that has faced challenges is the reform of the financial market, including the increase of the regulatory powers of the Federal Reserve Bank. This has been controversial and shows how complex and arduous it is to implement regulations that effectively restrict interest groups' influence over the lawmaking process. Additionally, legislation effectiveness has declined over the years, with Congressional productivity decreasing significantly, making policy implementations even more difficult.