And, as has been the case for most of the past week, the answer is: little, if any.
Now, a caveat applies. Since the speeches come so late in the evening, there really has only one wholly post-convention day in the sampling, and that was last night. And with that outsized tracking sample that Gallup employs (seven days), we are still at a point where the slight majority of respondents were queried about their preferences before Ann Romney and Chris Christie took the stage.
That said, there is quite a bit of evidence that the convention did not yield an outsized bounce for the Republicans, and will come well short of the 11-point bounce Romney's own campaign was flogging a while back.
On to the numbers:
NATIONAL (Gallup Tracking): Obama d. Romney (47-46)Thus, with three tracking polls, the current average is a Romney lead of 0.3 percentage points. On Tuesday, before the RNC began in earnest, these three tracking polls yielded an average which gave the president a lead of 1.0 percentage points.
NATIONAL (Ipsos/Reuters Tracking): Obama d. Romney (44-43)
NATIONAL (Rasmussen Tracking): Romney d. Obama (47-44)
Therefore, in the only apples-to-apples "bounce" comparison we can make, the bounce stands at 1.3 percentage points. That is, historically, a very weak bounce.
Also, given the trajectory of the data, it is somewhat hard to see how it will grow substantially. The momentum has been with Obama in the Ipsos/Reuters tracker over both of the last two days, as Romney has lost three points since Thursday's release. Gallup has been steady for three days, which hints that if there is any positive movement towards Romney in the last few days of polling, it has been quite muted. Only Rasmussen (perhaps predictably) is seeing real movement for Mitt Romney.
And if anyone needed any further reason to be skeptical of the House of Ras, look at what they released today:
After falling for two straight months, the number of Americans who consider themselves Republicans jumped nearly three points in August.So, in summary, the House of Ras sees a likely electorate, in a presidential election year, of GOP +4. The only problem? Exit polls show that a presidential electorate with more Republicans than Democrats has not occurred in the past 35 years. Add that to a pretty formidable pile of reasons why it is pretty easy to accuse Rasmussen of having their thumbs (and forefinger, and middle finger) on the scale when they assess the state of American politics.
During August, 37.6% of Americans considered themselves Republicans. That’s up from 34.9% in July and 35.4% in June. It’s also the largest number of Republicans ever recorded by Rasmussen Report since monthly tracking began in November 2002. The previous peak for the GOP was 37.3% in September 2004. See History of Party Trends.
The GOP now holds a partisan identification advantage of 4.3 percentage points. That’s the largest advantage ever held by Republicans and the largest for either party since April 2010.