Comprehensive tax reform is not on the list of things legislators expect to accomplish as they head back to Washington today for a month before breaking again to campaign in October. It's a long shot in any year, never mind an election season; the tax code hasn't been overhauled in three decades and recent attempts have gone nowhere.

Nevertheless, hope springs eternal. House Republicans have come up with a plan they say will boost savings and business investment by slashing corporate taxes and simplifying personal income taxes enough to fit on a post card. The progressive-leaning Institute on Taxation and Economic Policy finds that the plan will cost $4 trillion over 10 years and benefit only the super-rich; the conservative-leaning Tax Foundation argues that the resulting economic growth will cancel out nearly all of the losses. (That's what conservatives said in the 1980s, too, if you've been following along.)

The plan, however, is notable more for what it doesn't contain than what it does contain. Starting with the lack of a carbon tax, which is usually seen as the most efficient way to price in the environmental costs of burning fossil fuels.

OK, that's not all that surprising for a plan by Republicans, who've never shown much concern for curbing or mitigating the impact of global warming. But something has changed in recent years: The world's biggest oil companies have started to come around to the idea that they might have to deal with a price on carbon, which might give them an advantage over even-dirtier coal. Even Exxon Mobil, which for years funded organizations that fought the emerging scientific consensus that humans are changing the climate, has gotten behind a carbon tax.

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"Allow market forces to drive solutions," an Exxon spokesman told my colleague Chris Tomlinson in July. "In other words, if you put a price on carbon that is transparent and predictable and visible, the market will find ways to advantage lower-carbon energy sources, like it has with natural gas."

This time around, Exxon's own representative in Congress — Rep. Kevin Brady of the Woodlands — is now head of the powerful House Ways and Means Committee, succeeding Paul Ryan, who left that seat to become speaker of the house. It's his job to shepherd the plan through whatever political reality emerges after the November election.

He's taken $275,500 from the oil and gas industry this cycle, including $10,000 directly from Exxon (and perhaps more, through various PACs). So, what does he think about the idea of a carbon tax? Faced with the question in an interview last week, Brady pursed his lips and shook his head.

"Don't support it," he said. "Very little public support for it. Certainly very little legislative support."

Raising the price of energy, Brady said, just isn't going to fly. But what if, as many organizations backing various forms of carbon pricing have proposed, the proceeds from carbon taxes are redistributed back to citizens? That's how Alberta is handling its new price on heating and transportation fuels, in order to mitigate the impact on low-income families. And polls have shown majority public support for carbon taxes when the proceeds are either redistributed or used for alternative energy.

But Brady isn't convinced.

"In my view, we're creating a carbon tax that my guess is won't be revenue neutral, will be a net significant tax on energy in America, is bad for the economy, bad for families, bad for business," he said.

The most in-depth, unbiased studies of what impact a carbon tax might have — such as this one, by the Washington, D.C.-based energy think tank Resources for the Future — find that's simply not true, especially if revenues are used to reduce other taxes on activities we want to encourage, like employment and investment.

Now, it may be that energy companies are pushing carbon taxes in public while discouraging them in private, which would align with their giving patterns in recent years. At this point, that's the only way to explain continued GOP opposition to a policy that's favored by businesses, economists, and environmentalists alike.