I'd argue that after being qualified to be president, the most important thing a vice presidential candidate needs to do is avoid being a liability. See Eagleton, Thomas.

You will note that the Republicans avoided putting up another overt Big Oil ticket this year. None of their major contenders gloried in the sort of ownership by the energy industry that padded out Bush's and Cheney's resumes, and I'll bet McCain's vice presidential pick will also be a corporate crony of a somewhat less offensive stripe. Seen at the time as a boon because of a lifetime of experience (in squeezing the public and profiting from misery), a Cheney-like running mate would probably come over as a hazard, considering this year's fuel prices.

So why would Democrats be continually urged, when global warming is such a major public concern, to run a Big Coal ticket?

Indeed, it might look exactly that way if Obama picks any of Senators Jim Webb (D-VA), Evan Bayh (D-IN) or Sherrod Brown (D-OH) as a running mate against the only Republican in the country with a national image (undeserved as McCain's is) as an environmentalist. Why blunt an issue where Democrats have a wide advantage? Why make it more difficult to reach out to the 70 percent of evangelicals who believe that global warming is a threat and want the government to take action on it? And if he wants to reach Appalachia, why not go for the votes of appalachians who'd like to preserve their mountains and water supplies from the depradations of mountaintop removal?

I wrote previously about vice presidential nominee traits that might turn off Clinton's base of support, but this could be a similar turn off for Obama's own base, as well as independents and conservatives whose support he's said he wants to seek. All three of those coal state Senators, Webb, Bayh and Brown, have now signed a letter to Sen. Barbara Boxer (D-CA), chair of the Senate Committee on the Environment and Public Works, repeating the demands of the manufacturing and coal industries that future global warming legislation be even more favorable to their industries, include even more free giveaways, and provide more taxpayer support to save the future for coal.

Of the 18-29 year olds whose votes Obama won by large margins, 47 percent want the candidates to spend more time on climate change, while 65 percent want them to lay out more specific plans for cutting oil and gas use. I very much doubt that they support cuts in oil and gas consumption out of a considered interest in mining and burning more coal.

By contrast, Gov. Kathleen Sebelius (D-KS), though she also comes from a coal state, has vetoed new coal-fired plants three times, and as recently as this May. Sen. Patty Murray (D-WA) has an energy issues record that includes tireless opposition to drilling in the Alaskan National Wildlife Reserve (ANWR), favoring oversight to curb oil market manipulation, opposing a gas tax suspension as the cosmetic fix it was, and a zero rating from the National Mining Association. Candidates with records like theirs would shore up the good points of Obama's environmental record and demonstrate a willingness to stake out an independent path from polluting industries.

While Obama won praise for taking the harder, correct position opposing a scrap of the gas tax, he's come under fire for his support for coal-to-liquid technology. His record on coal is mixed to say the least, and I'd look to his vice presidential choice as a signal of his future intent.

Because everybody talks about it: if he decides that Clinton is an acceptable running mate, I'd make an exception by saying that the main thing it would indicate to me is that he thinks she'll actually help him win. She's the only potential veep of whom that might possibly (not that I know for sure) be true.

On the basis of this issue, though, she isn't the best pick. She supported scrapping the gas tax, and landed herself a 16 percent rating from that same National Mining Association scorecard* because the one vote she took in their favor, out of the six they evaluated, was in support of a coal-to-liquids amendment (which is identical to Obama's rating with them, and over the same vote). Neither of those things thrills me, but if she's the pick, my impression is that talk about her from both McCain and the media will be focused on other issues.

Anyway, I'm more interested in screening unsuitables out at this point than endorsing anyone for consideration. If potential choices are going to be criticized, and they will be, I'd far rather they be examined on progressive criteria.

* McCain got a 100% rating with the National Mining Association, for one vote in their favor out of six, a vote against union card checks -- he missed the other five votes they rated.