|Political polarization is widespread and well documented in Congress, and has been growing throughout the past two decades. This large divide is highly evident on climate change issues specifically, as almost all Democrats vote in favor of climate change policies and almost all Republicans vote against them. However, there have been several instances of party defection in Congress during climate change votes. In order to understand the nature of Congressional decision-making in a period of extreme partisanship, an investigation of party defection on climate change issues is warranted. In this paper, I analyzed Republican voting behavior on climate change policies from 107th-110th Congresses to demonstrate the factors that most strongly influence party defection. Using a logistical regression analysis and predictive probability coefficients to compare reelection considerations and political agenda considerations, I found that Congressional Republicans are most influenced by the desire to be reelected when considering how to vote on climate change policies. When a member's district was more ideologically conservative and he or she was not electorally vulnerable, the member would not break with the Republican Party and would vote against climate change policy. If, however, the Republican member represented a more moderate or liberal district and was electorally vulnerable, he or she was more likely to vote against the Republican Party and support climate change legislation. This paper supports further research, as more and more factors that influence Congressional voting behavior can be analyzed for their effects on party defection.