Nate Silver thinks it would be a political coup for Barack Obama to sign onto the "Gang of Ten" energy compromise bill in the Senate, and Joe Romm argues that even substantively, the bill is a good deal for Democrats. They both make strong cases. There's a basic inconsistency in the liberal narrative on drilling, which is that drilling is bad because it perpetuates our dependence on fossil fuels, but also that drilling is unwise because it won't produce very much oil. But, as Romm points out, if it won't produce much oil, how much can it perpetuate fossil-fuel dependence? And is it really worth taking a big political hit and passing up some genuine liberal goodies (repeal of some special tax breaks for oil companies, increasing funding for alternative fuels) just to keep the prohibition on drilling in place? It doesn't seem like it, especially since supporting the compromise would throw the spotlight back on John McCain's position: He opposes the "Gang of Ten" bill because it would repeal the oil-company tax credit. Try selling that politically: No to drilling, no to renewable energy investment, yes to Exxon.
For what it's worth, as I've written before, I think the drilling provision can also be justified on federalism grounds. To the extent that the risk of environmental damage as a result of drilling is concentrated locally--which it is, once you accept the premise that new coastal drilling won't produce enough oil to have a substantial climate-change impact--states should be able to decide for themselves whether they want to accept those environmental risks in order to get the economic benefits of drilling. And the "Gang of Ten" bill doesn't even go that far; it apparently keeps the drilling ban in place except off the coast of four states (Virginia, the Carolinas, and Georgia), which would get to choose whether to allow drilling. (And the Navy may veto it in the case of Virginia.) I'd say it sounds like a good deal for Democrats even if there weren't a political imperative to take the drilling issue off the table.
--Josh Patashnik