As of today, Gallup's tracking poll has Romney one point behind President Obama at 46% to Obama's 47%. This is 8 days from the commencement of the convention and two days post convention.
Gallup's 7 day tracking average AT THIS LINK from August 27th, the start of the Republican convention to August 28th has Obama 47% and Romney 46% and the same figures from August 25th to August 31st, the 31st being the last day of the convention.
The crucial figures are for seven days tracking August 26th to September 1st, which still has Obama 47% and Romney 46% thus showing no "bounce" at all. This is, according to Gallup's history below, the worst performance from a Republican candidate and the worst of any candidate except John Kerry.
In contrast McCain/Palin received a 6 point post convention lift.
U.S. presidential candidates historically have seen a median increase of five percentage points in their support in preference polls among registered voters after their party's nominating convention. The average is slightly higher, six points, due to the record 16-point increase for Bill Clinton after the 1992 Democratic convention.