Romney had been stalled at 45% for the previous 4 days, during which Obama had spiked as high at 50%. (Here's the running history of the polls, available to subscribers only.)
From the first link:
When 'leaners' are included, it’s Romney 49% and Obama 47%....
Perhaps most significantly, Republicans are once again more engaged in the election than Democrats. Forty-nine percent (49%) of GOP voters are following the race on a daily basis. Among Democrats, just 42% are that interested. Throughout 2012, Republicans have consistently held the enthusiasm advantage. However, for a few days following the Democratic National Convention in Charlotte, the president’s party caught up to the GOP on this important measure of potential turnout.