In keeping with the frenetic, rhetorical ping-pong that has marked virtually every moment of this young general election, Barack Obama gave a big energy policy speech in Las Vegas last month to counter the big energy speech John McCain gave just prior to it. Obama proposed a substantial federal investment in alternative energy sources, including wind power, solar power and biofuels, and he promised to hike fuel efficiency standards for cars and trucks (though he didn't say by how much). He has already proposed a cap-and-trade scheme with auctions for emissions permits, which are key to making any such scheme work. (John McCain's version of cap-and-trade does not include auctions.)

Nuclear power, however, does not figure into Obama's proposed alternatives to reliance on petroleum. On the contrary, he used the Las Vegas setting to hammer home, literally, his objection to McCain's proposal for the construction of 45 new nuclear power plants - a touchy subject in Nevada, given that the only site the US department of energy has designated for the storage of nuclear waste in the continental US (under the Clinton administration, incidentally) is the repository at Yucca Mountain, about 130 km from metropolitan Las Vegas.

Now, to be clear, Obama's energy programme on the whole is a sound and long-overdue, if not terribly ambitious, adjustment in the US approach to fuelling its economy. McCain's programme, by contrast, is a counterproductive, incoherent mash. But on the specific issue of nuclear power, McCain is exactly right, and Obama is badly wrong.

Nuclear power is green in multiple senses. The most important criterion by which to judge any viable alternative to petroleum is the magnitude of its contribution to global warming. Well, uranium or petroleum fission produces no carbon emissions whatsoever, since there is no carbon involved. The cooling process does produce water vapour, but water vapour and carbon dioxide are both greenhouse gases in the same sense that Roger Federer and I are both tennis players (and water vapour emissions, moreover, can be controlled). The environmental downsides of nuclear power are therefore not any more severe than other alternative energy sources, such as wind or solar power, and are arguably less severe than biofuels like the ethanol that Obama heartily supports. These energy sources all entail waste heat, produce solid waste and have other drawbacks - but the environmental drawbacks of all of them, nukes included, are quite modest.

From a fiscal perspective, nuclear power enjoys enormous advantages over other environmentally friendly energies. At their present state of technological development, nuclear reactors can already power large industrial societies. Wind and solar power are not there yet, and biofuels (particularly ethanol) are something of an embarrassing racket, being extraordinarily inefficient and requiring huge government subsidies to be propped up.

The case for nuclear power is even stronger when considering the weakness of the case against it, which rests largely on a series of panics 20 to 30 years old. For example, the Chernobyl disaster was the product of horrific Soviet mismanagement over the many years prior to the meltdown, followed by equally abysmal crisis management. It simply had nothing to do with the upkeep challenges of a modern nuclear plant. Worries about the impact of radioactive waste, by contrast, are at least marginally connected to real features of current nuclear plants, but they are wildly overblown. For one thing, the vast majority of nuclear waste - as much as 95% or more - can be reprocessed and reused, making it a truly renewable resource. For another, the technology required to render radioactive waste inert and harmless already exists, and it ought to be largely perfected by the time any new plants go online.

Then there are the silly and borderline mystical grounds for opposition to nuclear power, about which the less said the better (but let's be indulgent). Nuclear power plants, as the anti-nuclear movement frequently points out, use the same fuel sources and much of the same science as nuclear weapons. But that makes them as much like nuclear weapons as heart medications containing nitroglycerin are like dynamite. Alternatively, some anti-nuclear activists treat all nuclear technology as some sort of inherent transgression against nature. That argument relies on deeply reactionary concepts of "naturalness" and "unnaturalness" that also form the basis of opposition to any number of technologies that improve the quality of human life in countless ways. The argument against nuclear power as unnatural deserves no more or less respect than the arguments against childhood vaccination and stem-cell research as unnatural. Whatever else can be said about them, such sentiments have precious little to do with environmentalism.

Obama, however, brushed aside nuclear power as a policy option in approximately one half of one sentence in his speech, on grounds different from and even worse than any of the foregoing. McCain's "proposal to build 45 new nuclear reactors without a plan to store the waste some place other than right here at Yucca Mountain" makes no sense, Obama told the Las Vegas crowd. But did Obama propose some other site for storing nuclear waste or offer some further argument against nuclear power? No, he just dropped the subject.

In other words, even as he rightly mocked the risible gimmicks McCain has cobbled together as an ersatz energy policy, Obama's opposition to nuclear energy, in its entirety, is nothing more than a naked pander for Nevada's five electoral votes. For a politician ostensibly committed to environmentalism in general and curbing global warming in particular, omitting nuclear power from his energy programme - let alone doing so on no principle higher than grabbing votes - is irresponsible.