Boxer also pointed to the cost-containment mechanism, or "emergency off-ramp," as another key difference, characterizing it as a hybrid of other proposals that have called for a "safety valve" for industry should the cost of carbon credits get too high. How much of a sore spot this is for enviros depends in part on the price level at which the off-ramp kicks in -- Boxer's outline doesn't include a dollar figure, and she chose not state a figure in the press conference. She said the full text of her amendment would include a price range.

The senator elaborated further on the "transition assistance" the bill offers fossil fuel and heavy industry, noting that it will come in the form of allocated carbon credits. Handouts to the agricultural and building sectors, renewable energies, coal CCS, cellulosic biofuels, truck fleets, firefighters, state programs, etc., will come through the proceeds of permit auctions. She also talked up new language in the bill affirming that it will be "deficit neutral," imposing no net cost on the federal government.

Boxer acknowledged that the bill still isn't as strong as she'd like to see, noting that she'd push for emissions targets of 80 percent below 1990 levels by 2050 and a greater percentage of auctioned permits. But she believes that the bill in its current form stands a good chance of getting to the Senate floor. She pointed the rejection of Sen. Pete DeMint's (R-S.C.) proposed amendment to a budget bill, instructing Congress to hold off on enacting cap-and-trade legislation until China and India take more action. Sixty-one senators voted to kill the amendment -- including 12 Republicans.

"I haven't vote-counted, but I think I have enough votes for the motion to proceed," said Boxer.

"This bill will be opened to the floor, and there will be strengthening amendments, from my point of view, and weakening amendments," she added. "And we'll see where it all goes."