Just a minor adjustment to the overton window. It can be readjusted to give them all they want later on.
http://www.csmonitor.com/Money/Robert-Reich-s-Blog/2010/0618/The-Obama-plot-for-a-carbon-tax
New York Magazine’s John Heilemann thinks may be going on:
Lacking the 60 votes necessary for cap-and-trade, the administration plans to get behind a more modest conservation measure in the Senate, then push for a carbon pricing mechanism during the conference committee merger with the House bill — and do so during a lame-duck session after the midterms, when victorious Democrats will find it easier to make a tough vote and losing ones will be freed of political constraints.