Why Biden's Lead May Be Bigger Than The Polls Suggest

As of July 11th, former Vice President Joe Biden enjoyed his largest lead in the national polls (using the FiveThirtyEight polling averages) at 9.6 points.  Today, as I write this, Trump has cut Biden's lead down to 7.3.  

Or did he?

The FiveThirtyEight averages noted above are based on a preference for likely voter polls, when those are available. If likely voter polls are not available, registered voter polls are used.

During the spring and early summer, most pollsters focus their polling on "registered voters."  Starting in July or so, pollsters switch their attention to "likely voters," a narrower group of voters.  The reason why is that in every election, WHO turns out to vote can dramatically affect the results.  Sometimes, Republicans turn out heavily while Democrats stay home (see 1980 and 1994 for example).  Other times the opposite occurs.  (See 1974).  The concept of "likely voters" is the pollsters' effort to figure out those voters.

To calculate whether a person is a likely voter, pollsters look at a number of factors such as voting history and the person's answer to particular questions.  In a 2012 article, Pew Research explained the concept of likely voters:

Identifying likely voters is one of the most difficult aspects of conducting election polls. More respondents say they intend to vote than actually will cast a ballot. As a consequence, most pollsters do not rely solely upon a respondent’s stated intention when classifying a person as likely to vote or not. Most pollsters use a combination of questions that measure intention to vote, interest in the campaign and past voting behavior. Different pollsters use different sets of questions to help identify likely voters.

We use a lengthy set of questions to assign each respondent a score on the likely voter scale in our final pre-election poll. Earlier in the campaign, we often use a somewhat shorter version of the scale to identify likely voters. The set of questions may include some or all of the following:

• How much thought have you given to the coming presidential election?
• How closely have you been following news about the candidates?
• Do you plan to vote in the presidential election? How certain are you that you will vote?
• Rate your chance of voting in November on a scale of 10 to 1, with 10 being “definitely will vote” and 1 “definitely will not vote.”
• How often do you follow what’s going on in government and public affairs?
• Have you ever voted in your precinct or election district?
• How often would you say you vote?
• Do you happen to know where people in your neighborhood go to vote?
• In the last election, did things come up that kept you from voting or did you vote?

Even though most pollsters have now shifted to a "likely voter" model, many still offer results for "registered voters."   Comparing the two, Biden generally (but not always) does worse with the likely voter model, by 1 or 2 points, sometimes more.  In other words, Trump voters are slightly more "likely" to vote in most models so that could easily explain the slight drop in Biden's national lead.

However, due to our electoral college system, it is the state polls that matter.  But you see the same pattern with states, i.e. that Trump does better with "likely" voters.  For example, the recent ABC News/Washington Post poll of Florida has Trump up 4 points among likely voters, but behind 1 point when it comes to registered voters.  That same pollster has Trump up in Arizona by 1 points when it comes to likely voters, but Biden 2 points ahead when Arizonians who are registered to vote are considered. 

Again, while Biden's lead in state polling averages has slightly narrowed from the early summer, that may well be due to pollsters shifting to the "likely voter" model.

The problem with pollsters guessing which voters are going to show up to vote, it injects more chances for error into the development of polls results.  In 2016, likely voter screens overestimated the number of Democratic-leaning voters,, and, conversely, underestimated the Republicans, casting ballots in Pennsylvania, Michigan and Wisconsin.  While those polls results, which predicted modest Hillary Clinton wins in those states, were still well within the margin of error, turnout flipped those states, narrowly, to Trump.

But while trying to identify "likely voters" is always a challenge, it is necessary as election results inevitably depend on who turns out to vote.  But there is an exception to that  - those elections which are expected to feature heavy turnout among both Republicans and Democrats.  In those elections, which are rare, a better practice is for pollsters to focus on registered voters and omit the "likely voter" screen.  That is the election we are facing in 2020.  Believe the registered voter polls.

OOP's short takes:

• Amy Coney Barrett is the nominee...let the Catholic bashing begin!  Seriously, the Democrats need to be smart about their attacks on Barrett or they are likely to see a backlash among Catholics.  Former Vice President Joe Biden has made inroads with Catholics and no doubt he would hate to see those gains lost.  Biden cannot have a repeat of Democrats, such as Senator Kamala Harris, attacking Catholicism, even if indirectly.
• As a reminder, Harris had suggested a judicial nominee was too extreme and unfit to serve because because he had been a member of the Knights of Columbus.  The Knights, like the Catholic Church which sponsors the auxiliary organization, opposes abortion.  Carried to its logical conclusion, Harris was saying that anyone who chooses to be a Catholic is unfit to be a federal judge.  Fortunately for Biden, Democrats seem to have gotten the message not only to avoid Catholic-bashing, but to focus on threats to Obamacare rather than the abortion issue.  Preserving Obamacare is an issue that enjoys wide support that crosses party lines.  Abortion as an issue is more of a mixed bag.
• Speaking of abortion, from hearing Judge Barrett's previous comments about abortion, it sounds like her focus would be on cutting back on Roe v. Wade (actually the 1992 Planned Parenthood v. Casey decision has essentially replaced Roe which was handed down in 1973) to allow states to outlaw abortion during the second trimester.  While such a decision would still involve the Court rendering a policy decision arguably better left to legislative bodies, a focus on second trimester abortion instead of a complete overturn of Roe is better political terrain for Republicans.  Only about 10% of abortions happen during the second trimester and those abortions, while absolutely protected by Roe, are not popular. 
• Here is the thing about abortion polling: while Roe v. Wade is popular (it enjoys 2-1 support), when you ask about some of the types of abortions protected by Roe, such as second trimester abortions, public opinion quickly goes in the other direction.  (The obvious conclusion is that the public doesn't actually know what Roe stands for.)  This is why during a recent Hacks on Taps podcast, former Chicago Mayor and Democratic political strategist Rahm Emanuel counseled Democrats to talk about Roe and not abortion.   That is smart politics.