1. Introduction ResultsLiterature and Data Cited In recent years the House of Representatives and the Senate have been gridlocked. Recent examples such as the government shutdown or the open letter to the leaders of Iran are case studies into the ideological polarization of political parties, and the policy gridlock that results. In short, the “political center” has collapsed leaving little “space” for compromise between liberals and conservatives. One potential explanation for this is the proliferation of liberal and conservative interest groups in Washington, DC. Many interest groups “score” legislators according to whether they voted in favor or against the group on specific roll call votes. By announcing their vote preferences, Interest groups hope to influence the votes of Congress. In turn, legislators seek to maximize their score by voting with favorite groups to improve their liberal or conservative “credentials.” Recently, there has been a “fracturing” of the Republican party with extremist conservatives gaining a larger share of seats in the House of Representatives. This has caused an ideological polarization within the political party. Using Poole and Rosenthal’s party unity data that examines member Representative’s support for party votes, along with campaign contributions data from the Federal Elections Commission, my findings show that there is a correlation between the Republican members House of Representatives party unity scores and the average campaign contributions received from interest groups. This suggests that interest groups have also become more polarized over time. The polarization of interest groups is accompanied by the increasing polarization of members of Congress in the same policy space. While this does not establish a causal relationship, it is consistent with anecdotal evidence suggesting that interest groups have become centers of gravity pulling members of Congress to the ideological extremes. Conclusions Campaign contributions matter. Analysis of the data shows that there is a positive relationship between the average campaign contribution that interest groups donated had an impact on the unity of the Republican party from the 109 th through the 112 th Congress. The correlation of party unity with campaign contributions does not show causality of the polarization in the Republican party. Other political trends were occurring during the time such as the election of President Barack Obama – which provided fuel to the ideological polarization of the Republican party through case studies such as the Tea Party led “Birther Movement.” From the end of the Bush-era politics of the 109 th Congress – which was plagued by the Hurricane Katrina scandal and the start of the descent for the Republican party, the number of campaign contributions received by members of the House of Representatives declined – and so did party unity. It is interesting to note the major spike in campaign contributions during the 112 th Congress correlating with a major spike in party unity. This was likely fueled by ongoing debates over the introduction and passage of the Affordable Care Act during the 112 th Congress. Christopher Hare, Keith Poole (2013), The Polarization of Contemporary American Politics. University of Georgia. URL: http://voteview.com/pdf/The_Polarization_of_Modern_US_Politics.pdf Federal Election Commission (2012), Metadata 2005-2012: Committee’s Master List, Candidate’s Master List, Contributions to Candidates, Contributions by Individuals, Operating Expenditures. URL:http://www.fec.gov/finance/disclosure/ftpdet.shtml Keith Poole, Jeffrey Lewis, James Lo, Royce Carroll (2011). Scaling Roll Call Votes with wnominate in R. Journal of Statistical Software, 42(14), 1-21. URL http://www.jstatsoft.org/v42/i14/. http://www.jstatsoft.org/v42/i14/ Keith Poole (2008), The Roots of the Polarization of Modern U. S. Politics. University of California San Diego. URL: http://voteview.com/pdf/Revista_de_Ciencia_Politica_Essay_2008.pdf Keith Poole (2015), Party Unity Scores for Democrat and Republican Members of Congresses 35 - 113 (1857 - 2014). URL: http://voteview.com/Party_Unity.htm Acknowledgements I would like to thank Drs. Sean Q. Kelly and Geoff Buhl for allowing me the opportunity to work with their research linking interest groups and political polarization. I would also like to thank the Student Research Steering Council for the opportunity to be a member of the Interdisciplinary Research Learning Community of CSU Channel Islands. This has been an invaluable experience in understanding and performing research first hand. I look forward to digging deeper and discovering more. In addition, I want to thank the Western Political Science Association for allowing me the opportunity to present this research. Further Research I would like to continue future research into mapping the interest group universe that has a positive correlation with the unity of the Republican party, and the increasing ideological polarization being noticed. It would be interesting to examine if there is any link between business being done in a Congressional member’s district by a contributor to an interest group, and the increasing polarization of the Republican party. Further analysis could determine the underlying linkages between members of Congress and the financiers of the major contributing political interests groups. It would also be interesting to map if there is any correlation between the party polarization and the rising major contributing interest groups to see if “grassroots” lobbying is opening the door for more extreme conservatives. Politics to the Extreme: Polarizing Interest Groups Cordell Tarrant Dr. Sean Kelly California State University Channel Islands Methodology Data was compiled from various authors of datasets. The Federal Elections Commission provided data on interest group contributions to individual candidates during the 109 th, 110 th, 11 th, and 112 th Congressional election years which included data on candidate identification, candidate primary PAC, contributions from individuals to PACs, contributions from PACs to candidate primary PAC. The Library of Congress provided data on Congressional members including party, state, and district. Poole and Rosenthal’s DW-Nominate algorithm provided the mean voting ideology for Republican House members from 1945 through 2012; Poole and Rosenthal’s data also provided the number of supporting party votes and total party votes cast for House of Representative members since 1945. This data was compiled through Microsoft Excel, SPSS, and R Statistical Software. Using regression analysis, I compared the effect of Campaign Contributions (independent variable) to the member Party Unity score(dependent variable) to determine the statistical significance of the impact Campaign Contributions received from interest groups have on a representative members choice to vote along party lines.