It all depends on what the meaning of the word "is" is, and the non-establishment clause is just that: Government can't create or favor a religion. That doesn't banish religion from the political marketplace of ideas, and if they'd intended it to do that they would have written the Constitution so it did. It's not like they didn't spend months arguing about the thing and THEN tack on no less than eleven amendments (they considered twelve, and the last was only passed about a decade ago).

What's infuriating here, and drives the INTELLIGENT Tea Party members as well as O'Donnell, is that the lawyers know all this and are pretending they don't. Coons and everyone else keeps mentioning Jeffersons letter to the Baptists like, well, like it came down from Mt. Sinai, and like some arcane bit of lawyer lore they're deigning to share (though EVERYONE but stupid people know already). It's not part of the Constitution, any more than the Treaty of Tripoli is (though that at least has the merit of being US law). The arguments ARE tired, but they're also well known, and pretending not to remember them or that the whole debate is insipid insults not only O'Donnell, but every person they (which includes Coons) expects to believe it.

In terms of the actual debate, I'd say she did pretty well, though she was very vague on the Fourteenth Amendment question and only (but strongly) IMPLIED support for the Sixteenth. In fact, to be honest, most of Coons arguments were essentially ad hominems, because he didn't bother supporting any of them or answering questions, he just lambasted her as stupid, and the separation of church and state debate is a fine example. She kept hammering him about whether it's in the First Amendment (which he and all of us know it's not) and he kept clumsily dodging back to the phrase itself so he could talk about Jeffersons shopping lists, doodles of Sally Hemmings and other private correspondence that's not US law, let alone in the Constitution. Yes, it's a "long settled" legal principle because people like to refer to the letter and the Treaty of Tripoli (neatly making both American conservatives AND liberals anti-religious) but O'Donnells whole point (and that of many like her) is that it's not in the Constitution, and consequently if it's in CONFLICT with the Constitution the latter has precedence. That's the whole basis of judicial review, why US laws can be challenged in court, and every time a verdict is appealed to the SCOTUS that's part of the basis. It doesn't matter if a dozen federal courts ruled one way if they violated the Constitution doing it.