Environmentalism in US politics

One of the most controversial issues in environmental politics today is the Keystone XL pipeline, which would replace an existing pipeline, but has become a major political issue due to the environmental concerns associated with its construction. The proposed extension would run from Alberta, Canada to Nebraska, and then down to the Gulf Coast to transport oil overseas. However, the pipeline has been blocked by the Obama administration due to the proposed pipeline running through environmentally sensitive areas in Nebraska, and through a Sioux reservation in South Dakota. The Obama administration can block the pipeline due to the fact it runs across an international border, so it requires presidential approval. At the same time, the pipeline has become in effect a proxy battle between Republicans and Democrats over the issues of climate change and the merits and weaknesses of its economic and environmental impact. Republicans and some centrist Democrats support the proposal due to the promise of jobs it would bring (roughly , while the President and the liberal wing of the Democratic party oppose the pipeline due to their concerns over the environmental impact. The pipeline has been an issue over the last two election cycles, and is currently the central issue in the Senate election in Louisiana. Senator Mary Landrieu (a Democrat) is a supporter of the pipeline due to the oil industries size in Louisiana, and has been trying to bring up a vote in Congress on the issue before her runoff election in December. However, in recent days the Obama administration has indicated it would veto a pipeline, in effect leaving Landrieu out in the wind.