There is reason to think so:

Congrats, David Corn! Chait admits a mistake:

I’ve been wrong before, and I’ll be wrong again, but I may never have been as wrong as I was when I initially predicted that Mitt Romney’s heinous diatribe against 47 percent of America would have little direct impact on the election. It’s an absolutely crushing blow. Obviously it doesn’t guarantee his defeat — if a secret video surfaces depicting Obama promising to impose Sharia law in his second term, Romney will stand a good chance of coming back — but it destroys his public standing in ways that make a comeback nearly impossible.

Silver notes that since the tape was unearthed "Obama has gained further ground in the polls." He cautions that it's "hard to tell whether this recent gain for Mr. Obama reflects the effect of the '47 percent' comments specifically" but he also points out that "the most typical pattern after a party convention is that a candidate who gains ground in the polls cedes at least some of it back."