How about this for an all-of-the-above strategy: Approve the Keystone XL pipeline AND put a price on the carbon it emits, as well. This way there is something a lot of people can agree on and something a lot of people can disagree about -- often the only way to get something done in modern-day Washington.
Of course, President Obama has the authority to approve the pipeline without Congress. The path to a carbon tax goes through Congress which requires substantial backroom bargaining. Is he up to it? Do fossil fuel interests want the pipeline THIS much?