National Polls vs Ohio Polls: Which Are Right?

By Josh Jordan

Ever since the first debate in Denver, Mitt Romney has been on an upward trajectory in the polls.  While he has leveled off somewhat over the last week, nationally he has turned a four point deficit into a one point lead.  The lead actually jumps to two points if you only include the eight most recent national (non-online) polls.  In those polls Romney leads independents by an average of 17.5 points, which is a remarkable increase over the past month, and an amazing reversal of Obama’s 8 point lead with independents in the 2008 election. Romney has now been at or above 50 percent in Gallup for 12 straight days and Rasmussen for 5 straight days.

Those same national polls have a Democratic advantage of 4.4 points on average.  In 2008 Democrats outnumbered Republicans by 7 points and President Obama won the election by 7.2 (52.9-45.7).  The current polls have the Democratic edge dropping by just 2.6 points while Romney is up 9.2 points from McCain’s 2008 results.  This is an a shift due largely to independents, but also a worrisome picture for Obama that he is losing with Democrat turnout in these polls that is likely higher than what the electorate will look like after the votes have been counted.

While the numbers have brightened considerably for Romney nationally, he is still having a hard time breaking through in some of the key battleground states.  Ohio is of course the most closely watched of the battleground states, and Romney is currently behind in the Real Clear Politics average by 2.1 points.  At the end of September Obama held a much larger 5.6 point lead, but Romney has only been able to gain 3.5 points in Ohio where nationally he has gained five points. This has many wondering if Ohio is going to remain an impossible victory for Romney even with a 1-2 point lead nationally.

There are many reasons why it is very unlikely that Romney could win nationally by 2 points and still lose Ohio.  I went through some of them last week, but some of them could use a little more explanation.

In Ohio, Republicans tend to outperform their share of the national vote: In the last six presidential elections, only in 2004 has the Republican candidate performed worse in Ohio than they did nationally, and even that was only a .3 percent difference.  In the other five elections, the GOP candidate outperformed their margin of the national vote by an average of 3.1 percent.  While it’s clearly possible for Republicans to perform worse in Ohio than nationally, it is very difficult to imagine a scenario where there is more than a point difference between them based on past elections. History would suggest Romney could not be up 2 points nationally while being down 2.1 in Ohio, which would mean Republicans would be under-performing in Ohio by over 4 points.

Democrats national turnout advantage is usually bigger than their Ohio turnout: Not since 1996, during Clinton’s reelection campaign, have Democrats had a larger turnout advantage in Ohio than nationally.  In 2000 and 2008 Democrats were 2 points under their national turnout advantage and were actually 5 points under in 2004. Currently polls are showing an average Democratic turnout advantage of 6.3, which is 1.9 points higher than their current advantage nationally.

Both of these points are reasons why it’s more likely that either the national polls or Ohio polls are wrong rather than assuming they can both be right.  There is a big reason for this discrepancy, and that is the partisan makeup of the Ohio polls.

As mentioned above, in current Ohio polls Democrats have a party ID sample advantage of 6.3 points.  In 2008 Democrats had a 5 point turnout advantage in Ohio.  That means that while national polls have the turnout advantage down 2.6 points, in Ohio it has actually increased 1.3 points.  It is almost impossible to think that while the nationwide party ID advantage of Democrats has dropped since the wave election of 2008, Ohio has actually increased over the last four years.

If that’s not enough, the Ohio polls have actually become more Democratic since the post-DNC polls that gave Obama a significant bounce which led many pundits to declare Romney’s chances in Ohio DOA.  Of all Ohio polls from 9/7-9/19, Obama held an average lead of 4.2 points with a Democratic party ID advantage of 5.7 points.  Today Obama leads by 2.1 points with a party ID advantage of 6.3 points.  In the last month, while Romney has had surges in polls all over the country, the polling in Ohio has actually found more Democrats even while Obama’s lead was cut in half.

The biggest reason for this discrepancy appears to be due to early voting.  As many Ohio polls state more voters claiming to have voted early than the county records show, it inflates the likely voter pools with Obama voters pushing the Democrat’s advantage up as a result.  It is a big problem for pollsters as many respondents want to say the socially popular thing which is that they have already voted.  Unlike when respondents say they plan on voting, there are no follow-up questions to determine how likely it is that they have actually voted.  That puts them straight into the likely voter pool even though it’s clear that the amount of respondents that claim to have voted in the polls is much larger than the actual early voter turnout from the county records.  It would be reasonable to conclude that due to this the party advantage for Democrats would actually be lower, which would ultimately cut Obama’s lead in Ohio dramatically.

We’ll know in a little over a week which polls are right between national and Ohio, but history would suggest that come Election Day we’ll be looking back at the Ohio polls and trying to figure out how they could be so wrong.  With early voting becoming such a prevalent element of the Ohio election this year, it will be impossible to know just how much it is incorrectly impacting the polls until the election is over.  Even more unlikely is imagining an electorate in Ohio that is more Democratic than it was in 2008, but without it Obama likely can’t win Ohio. After seeing Romney’s rallies and enthusiasm compared to McCain’s in 2008, it’s easy to understand why Team Obama is fighting so hard to control the narrative that only state polls matter, because that’s the only domino left to fall.