Let's play a game. See if you can tell the difference between a shrill professor and a couple of former Republican EPA chiefs when it comes to climate change. Here's the first:

A market-based approach, like a carbon tax, would be the best path to reducing greenhouse-gas emissions, but that is unachievable in the current political gridlock in Washington..... [W]e held fast to common-sense conservative principles -- protecting the health of the American people, working with the best technology available and trusting in the innovation of American business and in the market to find the best solutions for the least cost.

And here's the second:

Opponents of a strong policy to curb greenhouse gases tend to be fervent believers in the magic of market economies. Yet somehow their faith goes away when it comes to environmental issues. If you seriously believe in markets, you should believe that given the right incentives -- namely, putting a price on emissions, through either a tax or a tradable permit scheme -- the economy will find lots of ways to emit less. You should definitely not believe, as anti-environmentalists claim, that the result would be economic disaster.

Okay, I didn't make that very hard. The first comes from the joint New York Times op-ed by ex-EPA heads William Ruckelhaus, Lee Thomas, William Reilly and Christine Todd Whitman, and the second from Paul Krugman. Taken together, they're a remarkable artifact into the political history of the past few decades.

See, things that used to be "conservative" ideas, like cap and trade or Obamacare or monetary stimulus, have become "liberal" ones, all while conservatives themselves have moved further and further right. That's what happens when you view negotiation of any kind as an ideological betrayal -- you abandon your ideology. You stop being the party of markets, and become the party of whatever-the-Democrats-are-against (and your donors are for). It's why, as Ezra Klein points out, the idea of the political "center" is such a canard.

And it's how Paul Krugman ends up sounding like a Republican. Or Republicans ended up sounding like Paul Krugman.

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