The Generic Ballot and the Dem False Positive?

What can I say? I feel like spreadin' sunshine today.

Interesting perspective on the generic ballot question, historically:

There has been a long-term tendency for Democrats to do better on this generic ballot question than they in fact do at the polls, so considerable care is required in thinking about this number. If a Democratic lead in the Generic Ballot were sufficient for control of the House, the Democrats would have won the House in 5 of the last 6 Congressional elections, including 1994! The trend estimates for each year, as of election day are:

2004: -1.07
2002: +1.49
2000: +5.26
1998: +8.03
1996: +5.45
1994: +3.35

Dems are up about 6 today, according to the three biggies from the weekend. Polipundit extrapolates, but that seems awfully optimistic.

Jay Cost had this to say about the generic ballot earlier this year, when it was showing a 14 percent Dem edge (emphasis mine):

What do I mean by "the skew?" I mean the following: the generic ballot persistently overestimates the size of Democratic support and persistently underestimates the size of Republican support. That means that pundits, insofar as they are relying upon the generic ballot, follow suit. However, we do not have to. If we have a reasonable expectation of what that skew will be - we can make a prediction about what will occur in November. All we have to do is subtract the amount of inflation from the Democratic majority.

Currently - the average June/July Gallup generic ballot of "national adults" shows the Democrats leading the GOP 51.8% to 38.4%. If we take only the people who are registering a party preference (what is known as the "two-party vote"), we can see that the Gallup generic ballot shows the Democrats leading 57.4% to 42.6% among people who prefer either the Democrats or the Republicans. That amounts to a very hefty 14.8% lead.

But this does not factor in the skew.

Historically speaking, when the Democrats have that kind of edge in June/July, by November their victory in the popular vote "shrinks" to a much more modest 51.75% to 48.25%.

In other words, today's Gallup generic ballot does not predict a Democratic blow-out. Not at all. It predicts another squeaker on the order of Bush v. Kerry. Bush's share of the two-party vote in 2004 was 51.2%. Kerry's was 48.8%. Michael Barone's "49-49 Nation," if you believe the generic ballot, has not actually gone anywhere. This year will be Round 3.