Those of you who read TDS’ Swing Voter roundtable earlier this year will remember that there’s a lot of disagreement about how to define swing voters. But such disagreements tend to shrink in the course of actual campaigns, as, gradually, the universe of potentially persuadable and motivatable voters converges with “undecideds.”
In his Wall Street Journal column today, Karl Rove, casting about for reasons to be optimisitic about John McCain’s campaign, suggests that there are “probably more undecided and persuadable voters open to switching their choice than in any election since 1968.”
At FiveThirtyEight.com, Nate Silver decided to test Rove’s assertion with actual data. Using the “unaccounted for voter” percentage in the last Gallup Poll (chosen because it’s been around forever), Silver compares that to the number at roughly the same date in earlier election cycles, and concludes:
In the Gallup tracking poll that straddled October 1st, 8 percent of voters were unaccounted for. This figure is significantly higher than 2004, an unusually partisan election in which just 2 percent of voters were unaccounted for. But, it was no higher than 2000 or 1976, and lower than in 1988. On average, since 1936, 6.8 percent of voters were unaccounted for in the Gallup poll as of October 1st, as compared this year’s 8 percent; the difference is not statistically significant.
To determine “persuadable” voters, Silver looks to the Pew Research poll’s numbers for people who have “decided against” one or the other candidate, indicating they are not open to further persuasion. The results are pretty much the same as with “undecideds”:
[A]s of Pew’s most recent survey from late last month, 42 percent of voters said they had decided against Senator McCain, and 37 percent said they’d decided against Senator Obama. This leaves 21 percent of voters who are theoretically open to either major party candidate. We can compare these to the Pew numbers released in Early October 1992, Late September 1996, Early October 2000, and Early October 2004….
This year’s numbers are right in line with past elections, again with the mild exception of 2004, when an unusually high fraction of the electorate had ruled out either George Bush or John Kerry. And remember, more voters have decided against McCain than Obama. The candidates to exceed the 42 percent of voters who have thus far said “no how, no way, no McCain” were George Bush, Sr. in 1992 (46 percent), Bob Dole in 1996 (44 percent), and John Kerry in 2004 (45 percent), all of whom lost their elections.
It’s possible, though not likely, that the undecided or persuadable vote could go up or otherwise change at some point between now and election day. But its current size and shape is not, contra Karl Rove, grounds for belief that Obama’s current lead may not be as significant as everyone thought.