The Steel Magnolia wrote:On topic - ASB, FiveThirtyEight is showing Obama at a 67.9% chance of winning, and 293 Electoral Votes. This seems remarkable from a single debate performance - is this sort of decline in the polls common after a debate loss, and why is it that we're not seeing any huge decline in the post-debate "bounce"?
Larry Sabato addressed this issue in a recent blog post. Since the data Sabato presents is not as clear as it might be, here's a modified version of his table:
Election | 1st Debate | Poll Before | Poll After | Winner | Net Gain |
1960 | Sept. 26 | Nixon 47-46 (Sept. 14) | Kennedy 49-46 (Oct. 2) | Kennedy | +4 |
1976 | Sept. 23 | Carter 51-36 (Aug. 30) | Carter 51-40 (Sept. 27) | Tie | N/A |
1980 | Oct. 28 | Carter 45-39-9 (Oct. 27) | Reagan 46-43-7 (Nov. 2) | Reagan | +9 |
1984 | Oct. 7 | Reagan 55-39 (Oct. 1) | Reagan 58-38 (Oct. 17) | Mondale | -4 |
1988 | Sept. 25 | Bush 49-41 (Sept. 11) | Bush 47-42 (Sept. 28) | Tie | N/A |
1992 | Oct. 11 | Clinton 51-33-10 (Oct. 10) | Clinton 47-32-15 (Oct. 14) | Perot | +9 |
1996 | Oct. 6 | Clinton 54-35-5 (Oct. 5) | Clinton 51-37-6 (Oct. 14) | Tie | N/A |
2000 | Oct. 3 | Gore 47-39-3 (Oct. 2) | Tie 43-43-4 (Oct. 6) | Bush | +8 |
2004 | Sept. 30 | Bush 53-42 (Sept. 26) | Bush 49-47 (Oct. 3) | Kerry | +9 |
2008 | Sept. 26 | Obama 48-45 (Sept. 25) | Obama 49-43 (Sept. 29) | Obama | +3 |
Judging from the historical record, the winner of the first Presidential debate has usually (85.7% of the time) enjoyed a "bounce" of between 3-9%, with 5.4% as the average gain.
That said, I'd like you to notice the following:
Election | 1st Debate | Poll Before | Poll After | Pre-Debate Leader | Net Change |
1960 | Sept. 26 | Nixon 47-46 (Sept. 14) | Kennedy 49-46 (Oct. 2) | Nixon | -4 |
1976 | Sept. 23 | Carter 51-36 (Aug. 30) | Carter 51-40 (Sept. 27) | Carter | -4 |
1980 | Oct. 28 | Carter 45-39-9 (Oct. 27) | Reagan 46-43-7 (Nov. 2) | Carter | -9 |
1984 | Oct. 7 | Reagan 55-39 (Oct. 1) | Reagan 58-38 (Oct. 17) | Reagan | +4 |
1988 | Sept. 25 | Bush 49-41 (Sept. 11) | Bush 47-42 (Sept. 28) | Bush | -3 |
1992 | Oct. 11 | Clinton 51-33-10 (Oct. 10) | Clinton 47-32-15 (Oct. 14) | Clinton | -3 |
1996 | Oct. 6 | Clinton 54-35-5 (Oct. 5) | Clinton 51-37-6 (Oct. 14) | Clinton | -5 |
2000 | Oct. 3 | Gore 47-39-3 (Oct. 2) | Tie 43-43-4 (Oct. 6) | Gore | -8 |
2004 | Sept. 30 | Bush 53-42 (Sept. 26) | Bush 49-47 (Oct. 3) | Bush | -9 |
2008 | Sept. 26 | Obama 48-45 (Sept. 25) | Obama 49-43 (Sept. 29) | Obama | +3 |
That's right: 80% of the time, the candidate when first debate took place lost ground in the polls; the average effect was a loss of 3.8% for whomever was leading in the polls at the time of said first debate - an effect that seems pretty consistent with what we've seen this year.
What's still more interesting, though, is that even debates which ended in a tie worked to the benefit of the trailing candidate: In 1976, President Ford gained 4% on Jimmy Carter even though their first debate was considered even; in 1988, Mike Dukakis picked up 3% from his initial tied debate with Vice-President Bush; and Bob Dole picked up 5% on President Clinton in 1996 even though their first debate ended in a tie.
As for the duration of these post-debate bounces, it's really hard to say. Conventions don't have the viewership of a debate, and historically are held several weeks before the fall campaign season; the last two years are really atypical in having both conventions literally bracket the Labor Day holiday that has - in the past - marked the traditional start of the Presidential race's home stretch. Debates, OTOH, tend to occur in clumps, with anywhere from 4-10 days between each meeting; this means that there isn't really enough time for each debate's "bounce" to fade before the next one hits.
The real test will come after the last debate; two weeks will remain from that point on, and those two weeks could see the winning candidate's edge drop away - although it should be kept in mind that the debates - unlike the conventions - are capable of making a permanent change in the public's perception of one or both candidates; in that sense, at least some of the winning candidate's post-debate "bounce" might endure.




