Why Obama's Going to Win

Nate Silver's analysis of state polls shows Obama will win the necessary majority in the Electoral College.

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So who's got the edge going into Tuesday's election? Over the weekend the New York Times's Nate Silver (about whom I apparently haven't written enough today) had a little noticed but instructive factoid about the reliability of state level polls in the final stretch before the election. What it boils down to is this: If history is any guide, Barack Obama really does have a near-insurmountable lead with six days left.

Silver wanted to figure out how often presidential candidates have blown leads in state level polling in the last 10 days before an election. Happily he's in a position to answer the question given his website's database of polling results. He crunched the numbers and found 44 instances since 1980 where state polls showed a presidential candidate with a single-digits lead over their opponent in the final 10 days before the election.

[See a collection of political cartoons on the 2012 campaign.]

Here's what he found:

Historically, this two- to three-point range has been something of an inflection point. Poll leads of 1.5 percentage points or less have been very tenuous and have not conveyed much advantage.

On the other hand, there was not a single instance in the database where a candidate lost a state when he held a lead of more than 3.5 points in the polling average at this point in time. (Bill Clinton, in 1992, lost Texas despite leading George H.W. Bush there by that margin.)

To put it another way, if you look at his chart there are 14 instances where a candidate held an average lead of less than 1.9 percent in a state's polls; in eight of those instances, the candidate with the lead lost the state. In the other 30 instances, candidates who held an average lead of 1.9 percent or more won the state 29 times (Clinton in 1992 in Texas being the exception). To put greater mathematical precision on this, Silver uses a "probit regression model" (no, I haven't the faintest idea what that is either) to construct a graph which puts the chance of winning a state at a hair under 80 percent when a candidate holds a 2 percent lead in the polling average.

[See Photos of the 2012 Presidential Campaign Trail.]

So in how many toss-up states does either Obama or Romney currently have a margin of 1.9 points or more (and more importantly how many electoral votes do they bring)? Real Clear Politics currently rates 11 states as toss-ups. Obama holds leads of 2 percent or more in Real Clear's average of polls in five of them while Romney holds such a lead in only one.

Here are the figures:

I'll save you the math—Obama has leads of at least 2.3 percent in five states which bring with them a total of 70 electoral votes. If you add them to the 201 electoral votes from states which Real Clear ranks as leaning or likely Obama (places where, in their average, he holds a lead of at least 5.3 percent) then you are looking at a second term for President Obama.

[See a collection of political cartoons on Mitt Romney.]

There are of course a couple of caveats. First, this is all predicated on state polls being reliable. There has been a disconnect this cycle between national and state polls, with most national polls showing a dead heat race while state polls, as shown above, give President Obama a clear lead. The conclusion of the Silver post I quote from here is that historically state polls have a pretty good track record. But Real Clear Politics's Sean Trende has a must-read article today examining the disconnect and he makes a couple of good points:

Of the 14 pollsters producing national surveys in October, all but three were doing the same in 2004 (although AP used Ipsos as its pollster that year rather than GfK, and I believe a few others may have changed their data-collection companies). Of the 14 pollsters surveying Ohio in October, only four did so in 2004 (five if you count CNN/USAToday/Gallup and CNN/Opinion Research as the same poll).

Pollsters such as ABC/Washington Post, Gallup, Pew, Battleground, and NBC/WSJ are well-funded, well-staffed organizations. It’s not immediately obvious why the Gravises, Purple Strategies and Marists of the world should be trusted as much as them, let alone more. And since virtually none of the present state pollsters were around in 1996 or 2000 (except Rasmussen Reports, which had a terrible year in 2000 and has since overhauled its methodology), it’s even less clear why we should now defer to state poll performance based upon those years.

The other caveat is that, as with sports, they play the game on the field. All the expectations, percentages, and mathematical models in the world don't mean much unless people show up and vote.

But given the polling and the history, you've got to consider the president a strong favorite for re-election at this point.

  • Read Jamie Stiehm: Barack Obama Is the Calm After the Storm
  • Read Ford O'Connell: Barack Obama's Failed Campaign Strategy
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