In this article, excepted from Nature, large-scale work with DNA shows that there were at least three separate migrations from Asia, not the one big one that Clovis-first postulates.
Much more to the point, though, is this piece, in which DNA again, this time from Paisley Caves in Oregon, appears to show that there was a pre-13,000 year old culture that is also pre-Clovis. The authors of a piece in Science are taking a somewhat cranky line about it all, since they apparently got beaten up severely by the Clovis cult types (read: people whose reputations and bodies of research have been based on the Clovis-first assumption.)
If you want the quick cocktail-party sound bite, you can just say, "Well, of course Paisley Caves stratigraphy demonstrates that the Western Stemmed tradition pre-dates Clovis ... oh, you hadn't heard? Really?"
Anyway, poke around in the articles if you care for this sort of thing, but I won't be offended if you don't. As always, I'm fascinated by the resistance to change exhibited by people who are supposed to be trained to read the data and react with what Gene Wilder's Dr. Frankenstein character called "quiet dignity and grace."