Some observers are pointing this quote from John Kerry's acceptance speech...

You see that flag up there. We call her Old Glory. The stars and stripes forever. I fought under that flag, as did so many of you here and all across our country. That flag flew from the gun turret right behind my head. It was shot through and through and tattered, but it never ceased to wave in the wind. It draped the caskets of men I served with and friends I grew up with. For us, that flag is the most powerful symbol of who we are and what we believe in. Our strength. Our diversity. Our love of country. All that makes America both great and good.

That flag doesn't belong to any president. It doesn't belong to any ideology and it doesn't belong to any political party. It belongs to all the American people.

...Against the backdrop of the cover of John Kerry's book, in which Old Glory is being flown in a derisive, upside-down position.

You can read more comment on this here and here.

Flag issues helped due in Michael Dukakis in 1988, but since much of the support for the Democratic ticket is really an Anybody But Bush vote (i.e. New Jersey), it probably won't hurt Kerry. Still, don't expect any more flag references out of Kerry-Edwards.