Friday’s Rasmussen daily tracking poll (with leaners) has Obama 47 McCain 45. There have been several stories over the last month noting Democrats’ concern that Obama hasn’t separated from McCain. Here are just three reasons for the concern:   1. It’s 82 days until the election and lots can happen. Intervening variables probably have a greater potential for an adverse effect on the numbers of the lesser known candidate.    2.The worry that Obama was closer to Clinton in the polls preceding the post-Wright/bitter primaries than he was in the actual results (not true in every case — Obama slightly underperformed in the polls preceding the North Carolina and Oregon primaries, for example) and that Obama’s overperformance may be replicating itself against McCain. Consider: Rasmussen’s last poll in the swing state of Pennsylvania had Clinton 49 Obama 44 — a 5 point differential. The final results: Clinton 54.6 Obama 45.4 — a 9.2 point differential. The latest Franklin&Marshall poll in Pennsylvania has Obama up 5 points. If Obama is indeed overperforming again, McCain may have a shot at taking a state Obama absolutely cannot afford to lose (by the way — the poll/final results differential in favor of Clinton was 12.3 points in West Virginia and 11.6 points in Kentucky. The demographics of these two states aren’t appreciably different from those of much of Ohio, save for the Northeast).   3. Obama continues to lag behind the generic Democrat.   Obama remains the favorite. But the Democrats’ concern is not unfounded.