Olympia Snowe's departure from the Senate raises a challenging question: in 2012, what does it mean to be a moderate Republican?

Too often, the definition of "moderation" reduces itself to issues of abortion and sexuality.

Which maybe was workable enough before the economic crisis. Since 2008, however, this definition has to be considered obsolete.

Hypothetical question.

Who is more "moderate"?

A pro-choice Republican who favors cutting the top rate of income tax to 20%, protecting all current Medicare beneficiaries, and balancing the budget by cutting unemployment insurance, food stamps, and the earned income tax credit?

Or a pro-life Republican who favors leaving the top rate of income tax where it is, protecting existing programs for the poor and unemployed, cutting payments to Medicare providers, and balancing the budget with a VAT?

I recognize that neither creature exists in real-world politics. But think along with me.

If the most pressing and difficult question in public life is "How to share austerity?" (as Thomas Byrne Edsall intelligently argues in his new book), then surely a "moderate" is one who arrives at an intermediate answer to that most pressing and difficult question?

President Obama's answer to the question is to rely heavily on the lapse of the Bush tax cuts and to shrink the defense budget.

The predominant answer in the GOP is to heap all the burden of adjustment on the young and the poor—while offering the richest yet more tax cuts atop the Bush tax cuts.

Isn't a moderate then, whether Democrat or Republican, somebody who walks between those lines? If not, why not?