So much for the first serious attempt to pass a cap-and-trade bill aimed at reducing greenhouse gas emissions. The Lieberman-Warner Climate Security Act is dead, at least for now. On Friday morning, Democratic senators were unable to muster the 60 votes necessary to end a Republican filibuster.

Four Democratic senators voted with the Republicans: Louisiana's Mary Landrieu, North Dakota's Tim Johnson, South Dakota's Byron Dorgan, and Ohio's Sherrod Brown. Landrieu's vote is explained by Louisiana's extensive energy industry infrastructure. How the World Works is unsure why the Dakotas are a hotbed of anti-cap-and-trade sentiment -- but perhaps we can blame the billions of barrels of oil supposedly ready to be pumped out of the Bakken shale formation.

But what about Sherrod Brown? What does his vote signify?

Brown is one of the most liberal voices in Congress -- as Stephen Koff, blogging at Cleveland.com, observes, he has been "one of Washington's most outspoken critics of oil companies, pharmaceutical companies and corporations that sought higher profits at the expense of workers and the environment." He's also been one of the most prominent voices of anti-trade economic populism.

But he's been lobbied heavily, writes Koff, by corporations and trade groups "representing Ohio's steel, glass, chemical and other heavy industries," who fear higher energy prices as a result of a cap-and-trade bill. And in Ohio, one of the most economically hard-hit states in the nation, that argument may have been compelling.

Hard economic times are going to affect the calculus of global warming politics. The worse the economy performs, the more difficult it will be to pass any kind of legislation that threatens to raise energy costs. And while How the World Works has a lot of sympathy for those who argue that Republican scare-mongering about the economic impact of restricting emissions is grossly exaggerated, still, there's no question but that the entire point of cap-and-trade legislation is to make certain kinds of industrial activity more expensive. Ideally, Congress could compensate for the negative effect of such measures by bolstering safety nets and redistributing wealth, but pushing through such measures will require a different occupant of the White House and significant increases in Democratic congressional majorities.

Perhaps the reason why neither Barack Obama nor John McCain bothered to cast a vote in today's cloture motion -- even though both are on record as supporting the Lieberman-Warner bill -- is because they knew that there weren't enough votes to stop the filibuster, even with their help.

Or maybe they've got one eye on the all-important swing state of Ohio, where, if Sherrod Brown's vote tells us anything, economically stressed voters care more about the price of gas than the temperature of the planet.