Ross Douthat wonders whether Rick Santorum’s presidential campaign might be not “the last glimpse of the Republican past, but as a plausible sketch of the Republican future.” Douthat sees Santorum as what I would call a “Big Government conservative,” that is, a person who identifies as a conservative and supports a larger role for government in both the economy and culture.

Let’s try to put some numbers on Douthat’s speculation. A recent essay by James Stimson and Christopher Ellis provides useful data and analysis for this task. To use the Stimson-Ellis summary, we need to make the reasonable assumption that 20 percent of the nation identifies as “liberal” and 35 percent as “conservative.”

Stimson and Ellis find that about 10 percent of the nation identifies as conservative, affirms cultural conservatism, and rejects free market policies. Another 4 percent identify as “liberal”, support cultural conservatism, and reject free market policies. So the Santorum base, as it were, is about 14 percent of the population. However, this estimate assumes that people who identify as a liberal would vote for Rick Santorum. The actual Santorum base, in other words, is much closer to 10 percent than to 14 percent of the population.

Compare this range to other numbers indicated by Stimson and Ellis. About 13 percent of the nation identify as conservative and support free market policies. A little over 1 percent also identify as liberals and support less government control of the economy. Another 13 percent are consistent liberals in supporting both economic interventions and cultural liberty.

The Santorum base is certainly not a majority among conservatives; it is also not the largest group among those identifiers. Stimson and Ellis find that 29 percent of conservative identifiers support Big Government in the economy and the culture. That means 71 percent of conservatives do not support Santorum’s outlook. That hardly seems to be a foundation for a future GOP.

Perhaps Douthat believes that Santorum’s anti-free market policies will attract enough people in the nation as a whole to convince GOP voters that he (or someone like him) can win a general election. But about 50 percent of those who say they are conservative do not support cultural conservatism. Is it likely that the 45 percent of the nation that does not identify as liberal or conservative will be drawn to a party and candidates espousing cultural conservatism?