Steyer Tops Adelson in Superpac Political Donations

Will Steyer, a former hedge fund manager, has become a significant political donor, surpassing his pledge of $50 million to defeat Republican candidates. He has donated $55 million to his Next Gen Climate Action Committee since June 2013. This surpasses Sheldon Adelson's $50 million donation to Republican causes in 2012. Steyer is also known for his efforts to stop the Keystone Oil pipeline.

Who is Sheldon Adelson and how much did he donate to Republican causes in the 2012 campaign?

What is Steyer's stance on the Keystone Oil pipeline?