Sorry, Jim, the PUMAs are Dead

Over at the Campaign Spot, Jim Geraghty wonders how the new ABC/Washington Post poll could have the temerity to suggest that Barack Obama is winning more support among Democrats than John McCain is among Republicans:

The ABC/WashPost poll in late September found 86 percent of Republicans for McCain, 88 percent of Democrats for Obama. PUMAs don't exist anymore? Colin Powell and Christopher Buckley are leading the exodus of Republicans for Obama? I suppose it's possible, but I have my doubts.

I suppose I have my doubts too, except that this finding is now reflected in any number of polls. In fact, six of the eight trackers that published today included the support that each candidate is winning within his respective party. Let's take a quick look at those figures:

Support within own party:
Pollster             DEMS       GOP
Rasmussen            86         87
IBD-TIPP             88         83
Research 2000        87         89
ABC/Post             91         84
Zogby                87         84
Battleground         89         85

AVERAGE              88.0       85.3

2004 Exit Poll       89         93
2000 Exit Poll       86         91

Among Democrats, Barack Obama is now winning 88 percent support, comparable to John Kerry in 2004 or Al Gore in 2000. And there are a couple of points' worth of undecideds left in there, so it's possible that Obama could scrape up against the 90 percent number on election day.

By contrast, John McCain is winning the support of just 85.3 percent of Republicans, well down from Bush's 93 percent in 2004 and 91 percent in 2000. There are some undecideds in there as well, so his numbers should improve some, but McCain is likely to underperform Bush by several points.

This is really the key theme of the whole post-Lehman Obama surge. Between his more populist talking points on the economy, the backlash to McCain's attacks, and -- I'm guessing here -- a deep level of antipathy among Democrats toward Sarah Palin (Battleground has her favorability ratings at 12/78 among Dems), Obama has really brought the Democratic base home. By contrast, Obama's support among independents varies quite significantly from poll to poll, ranging from essentially even in the Rasmussen tracker to a +15 in Zogby.

Perhaps the more important question is whether, all else being equal, you would rather have a lead built upon support within your own party or built upon independent support. My guess is that the former is a bit more solid: Partisans turn out more reliably than independents, and change their minds less often.

And here's a really scary stat for McCain. If Obama wins by the same margin among Democrats that McCain does among Republicans (and to reiterate, right now Obama is doing a bit better within his own party), and Rasmussen's most recent party ID breakdown is correct (D 39.7, R 33.0, I 27.3), then McCain will need to win independents by about 20 points to earn a draw in the popular vote.