Specifying "Out of the Mainstream" for Analytic Clarity

I often read and hear Dems and liberals (not co-extensive sets) decry "extreme" conservatives, "extremism" and "out of the mainstream" positions held by conservatives. Recently, I particularly hear and read "out of the mainstream" applied to conservative positions on jurisprudence.

So we're not merely trafficking in rhetoric, but hopefully something closer to reality, why don't we clarify and specify the terms? Why not make these terms analytically distinct, and thus analytically helpful?

And since Dems and liberals make these statements about conservatives being "out of the mainstream," I thought it would be fair to give them first opportunity to define these terms to the Dem and liberal readers of Dignan's 75 Year Plan. Perhaps our readers can get the ball rolling and we can discuss back and forth until we reach agreeable parameters for the terms. Once we have the terms we can use them as a standard to assess all manner of actors in the political arena with a degree of objectivity.

Granted, these terms are relative terms so it is not possible to affix with precision the meanings and parameters of these terms. Perhaps the best we can do is arrive at a conventional account that will serve as a snapshot of the meanings of these terms in our cultural moment.

On with it. For a conservative legal eagle to be called "out of the mainstream," say, on abortion, what is the mainstream? What defines what is "mainstream" regarding abortion rights in our society and thus what is out of the mainstream regarding abortion? Most important of all, because we're talking about a democracy and governance of citizens' lives in the present, what percentage (roughly) of the populace must subcribe to a position to make the position "mainstream"? Correspondingly, how small a percentange of the populace is required to cross into "out of the mainstream" territory?

Again, absolute precision will not be possible but if our lefty readers will begin suggesting numbers and other aspects of defining "mainstream" and "out of the mainstream" perhaps we can get this discussion going. If we can skip power politics and rhetoric and have an actual fair, principled discussion, that would be helpful to all, yes? I say that to those readers on both sides who find it harder to resist inflammatory statements and rigid party-loyalty thinking. Let's be kind and let's really talk this one out.