This graph presents the pre-debate and post-debate trends in polls conducted during the 2004 election. RCP does not report whether the data represent registered voters or only likely voters for that year, so I have had to include both types of polls in the chart above. The change in the campaign’s trajectory after the September 30th, 2004, first debate was dramatic. Mr. Kerry erased nearly nine points from President Bush’s predicted margin in the polls on Election Day. Kerry also halted the President’s rapid gains in the polls; the daily rate of increase for George W. Bush between July 4th and September 30th was 0.12 percentage points per day, twice the rate scored by President Obama in 2008.
Unfortunately for Senator Kerry he never advanced any further in the polls after that. Kerry stemmed Bush’s advance but could not manage to pick up that last remaining two percent that would have brought him even with the President. Polls after the first debate average Bush+2 with no visible or statistically measurable trend. According to the 2004 polls, the campaign stagnated after the first debate.
Whether we might expect a similar pattern in 2012 cannot yet be determined. All we can tell at the moment is that Mr. Romney picked up almost as much ground (+6%) as Kerry did eight years ago (+8%). There is not yet enough data to tell whether the campaign will stagnate at the current small Romney lead, or whether the President might recover from the blow in the weeks ahead.