The conventions matter either a lot or not much, and it is difficult to say which, not just before the event but also after. Thank you to Larry Sabato for clearing that up. (Seriously, it's an interesting article: indispensable pre-convention prep.)
Recent history suggests that there is a better than even chance we'll be misled by the post-convention bounces in 2008. Yet forests will be lost to produce the newsprint for the stories about the overarching significance of 2008's post-convention bounces. And the "tubes" that comprise the internet (in the immortal description of now-indicted Alaska U.S. Sen. Ted Stevens) will be clogged with breathless analysis of the same numbers.
Well of course. That's why we're here.