I think (some) moderates do indeed stand on firm ground–at least the ones who are moderate for principled reasons rather than for political expedient ones.

The theoretical basis for moderate political views may perhaps be the work of philosophical pragmatists like John Dewey and Richard Rorty.

I do not know how to identify a moderate. My best guess is that a moderate is a person who has the good sense to recognize that the traditional characteristics of the two groups are purely arbitrary categories of preferences. The preferences represent demands of their neighbors and their government.
Being arbitrary demands, the moderate sees no logical reason why she should not demand a little bit from the conservative bag and a little bit from the liberal bag. For instance, upholding old-fashioned military subsidies is perfectly compatible with demanding educational subsidies — just like eating fruit (apple/cranberry sauce) with your meat (turkey/pork chops) is palatable to some people.

They just think that when you have a headache, you don’t down an entire bottle of pain killers. The dose makes the poison.

Those descriptions are pretty shallow and two dimensional. However, as broad descriptions go, they’re not bad.

Regarding moderates, I don’t really know. It really depends. I think some “moderates” are standing on principle, but I’m guessing most “moderates” are just trying to competing interests in an imperfect world.

But again, it depends on how we’re going to defend “moderate”. I’ll have to think a little more about it to give you a better answer.