The next U.S. president will favor a carbon cap. What effect this has on the race is anyone’s guess. 5

Now that John McCain is the presumptive Republican nominee, the shape of the debate over climate change takes on different contours. Hillary and Obama are offering substantively similar climate plans, so there's no need to wait for the Democratic contest to be decided before we start gaming out a few scenarios.

1) Will climate change take on more or less prominence as an issue in the general election?

Argument for less: with everyone preaching from the same book, the media sees no hay to make. This suits the candidates fine. McCain knows the topic alienates conservatives. Hillbama knows their policy position makes them look liberal and McCain look independent/centrist. Under different circumstances, the Dem could have tried to portray the Republican as reactionary, but no longer. Everyone changes the subject to war and the economy.

Argument for more: candidates might want to ignore the issue, but they won't be allowed to. Seeing the writing (now bold-print, 198-point font) on the wall for 2009, interest groups go nuts. Environmental Defense and the Competitive Enterprise Institute take out dueling ads in swing states. Slow-witted reporters find a story angle: whose climate change plan wrecks the economy more? "Energy independence" and "green collar jobs" become dominant buzzwords of the election cycle.

Safe prediction: an escalating contest to prove who loves biofuels the most culminates in one candidate chugging a gallon of ethanol on live TV.

2) With all candidates agreeing on the need for a carbon cap, will proposed legislation become weaker or stronger?

Weaker: with McCain providing cover on the issue, Hillbama and Democrats in general delightedly tack to the center. By erasing any difference between themselves and McCain, they hope to neutralize wedge issue politics and rob anti-environmental voters of a clear choice. McCain himself implicitly backs away from his previous commitments by ostentatiously bear-hugging a bunch of poison pills (nuclear energy, etc.) and daring his opponent to follow him.

Stronger: recognizing that most of the public isn't following the weedy details, candidates and lawmakers engage directly with the relevant interest groups. The policy momentum strongly favors greens, who are increasingly happy to let the question simmer until 2009. For its part, industry is newly ready to make concessions.

Safe prediction: the eventual legislation will contain provisions for creating jobs, battling terrorism, and whitening teeth.

Anyone care to place some bets?

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