According to E&E News, Dick Durbin, the Democratic whip in the Senate, is saying there aren't 60 votes in that chamber to overcome a filibuster and approve climate legislation similar to the draft bill Waxman and Markey just unveiled in House. To get a sense of how thorny this will be, Senate Republicans have recently been putting forward amendments to prevent cap and trade from even being considered this year. (That's curious: If they're so sure of their arguments that climate legislation will destroy the economy, why are they afraid of debating it?)

Meanwhile, North Dakota Democrat Byron Dorgan, who sits on the Senate energy committee, thinks it's unwise for the House to lump a cap-and-trade bill together with a bill to promote renewable power and efficiency and a bill to bolster the grid. He wants to do those all things separately, which would likely mean first the grid bill and energy bill (which should attract some GOP votes) in 2009, while carbon caps probably wait until 2010. But here's why Waxman and Markey want to lump them all together, from E&E Daily:

Going forward, Waxman and Markey are banking on a combined energy and climate bill to build support for their legislation. Aides explain that the measure offers a new way of thinking compared with previous and more limited attempts in the Senate. The economic models, for example, will show that combining cap-and-trade legislation with an RES and the energy efficiency programs can lower compliance costs for households and industry.

In other words, when the impacts of the cap-and-trade portions are tallied up by the CBO and other economic models, the projected costs will likely be lower when you include stuff like the efficiency and grid provisions—many of which could help reduce overall energy costs, even as the price of coal and gas goes up. By contrast, a bill that only has a mandatory carbon cap will seem a lot costlier.

Still, this could turn into a point of dispute between the House and Senate. One thing to observe is that the House has just one committee to deal with energy and climate matters—Waxman's committee—so it's easy to pack everything in, whereas the Senate has two relevant committees: Barbara Boxer's Environment and Public Works, which is drafting the cap-and-trade portions, and Jeff Bingaman's Energy and Natural Resources, which is working on the measures to promote efficiency, renewable power, grid infrastructure, and the like. So you could see more jurisdictional disputes in the Senate, making it trickier to cram everything into one big bill.

More: Dave Roberts makes the political case for a Big Bill strategy:

It's important to note that the cap-and-trade part of the package is by far the least popular and easiest to demagogue. So conventional wisdom has been that Dems should lead with the more popular energy and grid stuff. But those aren't a cakewalk either—there's plenty of regional opposition to renewable energy standards and a whole set of jurisdictional and local battles around the grid.

The fact is, doing these pieces separately would mean three, four, possibly five bruising legislative battles, culminating in a battle over cap-and-trade that, in my estimation, simply can't be won on its own in this Senate. No one in D.C. has the appetite for that, not this year.

So they've decided, uncharacteristically for Democrats, to double down. They are piling all this stuff into one big-ticket, high-profile, must-pass bill. Just as there will be "a healthcare bill"—and not four disparate, complicated healthcare bills only wonks can understand—there will now be a green economy bill. For it or against it.

--Bradford Plumer