Below is Gallup's seven day tracking poll. The site for further examination if required is AT THIS LINK
For the seven day ending on August 27th, the commencing day for the Republican convention in Tampa Romney actually had a one point lead over President Obama 47% to 46% as the dark green line on top of the light green line as the chart below indicates.
For the week which included the convention and two days subsequent to it, week August 27th to September 2nd, President Obama was in the lead again 47% to 46%. This 1 point decline is the worst of any Republican candidate since Gallup began these charts and is equalled only by John Kerry for the Dem's in 2004.
The Real Clear Politics tracking poll AT THIS LINK is only slightly better for Romney over the same period. He was behind pre-convention 46.8% to 45.7% and inclusive/post convention is behind 46.4% to 46.4% a rise of only 0.7 points, still the worst Republican performance.
If the Democrats get any rise at all from their convention, allied to President Obama's lead across the battleground states it will make Romney's task over the few week remaining extremely difficult unless there is some sort of Lehman Brothers disaster or "black swan" event.
Electoral-Vote.Com AT THIS LINK (with map) has President Obama in landslide Electoral College territory 332 EV votes to Romney at 206. This is approaching his margin over McCain which is achievable in the Electoral College but unlikely in the popular vote.