Tag Archives: Polls

THE GENERIC BALLOT: 18 MONTHS OUT

The 2020 elections are still 18 months away and yet pollsters are out in force, giving us just enough information to break out our crystal balls and make wildly irresponsible predictions. This is the second post in a three-part series looking at the Generic Ballot and it’s utility as an election predictor. You can read the first post in the series here


Last post I argued that the Generic Ballot — the polling question that asks respondents if they plan to vote for a Republican or Democrat for Congress — is fairly predictive of election results when the poll is taken right before or on election day. But what about a year and a half out, as we are now from the 2020 election?

Early Generic Ballot polling is tough to track down, but Real Clear Politics has aggregated such polls since the 2004 Bush v. Kerry presidential race. The sample here is very small, only four presidential election cycles, so adjust skepticism accordingly.

In the chart below, I have averaged the results of the first five Generic Ballot polls taken in an election cycle, starting 19 months out from the election1Notice that not every cycle has polling data going back 19 months before the election. 2004 in particular, lacks very early polling data..


Data: RealClearPolitics

In 2008, 2012, and 2016, the early polling was surprisingly accurate, missing real election results by a net average of only 1.7%. The 2004 election polling, though, breaks this trend. The earliest polling projected a Democratic win of 10%, but Republicans won the House Popular Vote by 2.6%, leading to a 12.6% polling miss.

Lacking more historical data, it’s hard to determine if the error in 2004 is an outlier or not. If it is, and early Generic Ballot polling is generally within 1 to 3% of real election results, we could say that the numbers we see now are predictive of what’s to come in 2020. And while control of the House could hinge on this 1-3% polling error, the Generic Ballot polls would still be able to show the world of possible outcomes and which is most likely.

If 2004 is not an outlier, though, and Generic Ballot polling really will miss the mark by double digits about a quarter (or more) of the time, the Generic Ballot this far out cannot show us the world of possible outcomes, or the likelihood of these outcomes. Predicting that the House Popular Vote could be anywhere between a net +6 for Democrats and a net +6 for Republicans does not narrow election outcomes in any helpful way.  Because we can’t determine how likely a polling error like 2004 is the Generic Ballot this far out it should not be treated as predictive.

With that caveat, here are all the Generic Ballot polls taken within the past two months from pollsters receiving at least a B- pollster rating by FiveThirtyEight. Note that Morning Consult and Politico have conducted all but one of these polls, which raises the probability that there is a consistent statistical bias in their results, meaning that the data should be treated with even more skepticism.


Data: FiveThirtyEight

Clearly, Democrats currently have a consistent advantage in the Generic Ballot, averaging out to 7%. And while, again, this is not predictive 18 months out from election day, it does expose three important things about the current political environment.

1) The wave that swept Democrat’s into power in the House in 2018 has not dissipated. In that election, Democrats carried the House Popular Vote by 8.6%. So, Republicans may have closed this gap by a point or two, but the pro-Democratic sentiment largely remains.

2) Most voters’ Generic Ballot responses are determined by their feelings about Donald Trump. His net approval rating during this two-month period has ranged from about -9% to -13%. Not exactly the same as Generic Ballot polling, but close enough to give the impression that Trump’s approval is a big factor in down ballot decision making (at least in polls).

3) The small gap between Trump approval and the Generic Ballot average is important, though. While most voters who approve of Trump will vote a Republican Representative, and voters who disapprove of Trump will vote Democratic Representative, there is a small number of voters who distinguish between the top of the ticket and down-ballot races, And while this population is small and shrinking, it still exists. When control of the House can hinge on just one seat, any swing can be determinative.

The big question is if Trump will be able to turn his poor approval rating around. He has been stuck around -9 to -13 for most of the last year. If he can pull it closer to even, Republicans have a good chance to win the Generic Ballot and to take the House. If he continues to slum it down near negative double digits, 2020 will almost certainly see continued Democratic control of the House, likely control of the Presidency and possible control of the Senate. That’s the order Democrats are likely to hold or take power: House -> Presidency -> Senate. It’s hard to imagine a world where Democrats win the Presidency and lose the House or where they win the Senate and lose the Presidency and/or House.

Control of the House, though, is not determine by the Generic Ballot or the House Popular Vote. It is decided district by district. Whichever party wins in a majority (or plurality if there are 3rd party winners) of the 435 House seats will hold the House. In the next post we’ll look at how closely the House Popular Vote correlates to seat allocation between the parties and what this means for the 2020 election. The big question we’ll aim to answer: how much do Democrats or Republicans need to win the House Popular Vote to take control of the House?

THE GENERIC BALLOT: PSEPHOLOGY’S CRYSTAL BALL

The 2020 elections are still 18 months away and yet pollsters are out in force, giving us just enough information to break out our crystal balls and make wildly irresponsible predictions. This is the first post in a three-part series looking at the generic ballot and it’s utility as an election predictor


Democratic presidential primary polls have been dominating election headlines, but some congressional polls have been been released too,  albeit to much less fanfare. We should probably ignore these polls — it’s too early for them to be predictive. Prognosticating off these preliminary numbers is rash, reckless and generally unwise. And so that’s exactly what we will do here in a three-piece series. This post will focus on how predictive the “generic ballot” is on, or close to, election day. The next post will look at how valuable these numbers are now, given that the election is still a year and a half away. The last will look at the relationship between popular vote and seat apportionment.

In “generic ballot” polls, respondents are asked to choose between a nameless Republican and Democrat for Congress. Gallup asks it this way: “If the elections for Congress were being held today, which party’s candidate would you vote for in your congressional district — the Democratic Party’s candidate or the Republican Party’s candidate?” It measures national support for the two parties without some of the baggage carried by their polarizing national figures (think Donald Trump, Bernie Sanders, Mitch McDonnell, Nancy Pelosi, Alexandria Ocasio-Cortez, etc.). It can also bring forward nuanced voter trends. For example, some voters might support a Democrat for President but Republican for House because they want the grinding impotency of split government. Another might vote the same way but because they support Trump but want continued House oversight. Another might choose to reward the current power dynamic because the economy is strong.

Final generic ballot polls — the ones taken within a few days of the actual election — are a better indicator of election outcomes in midterms years than in presidential years. Since 1948, the final generic ballot has missed the real midterm vote by an average of only 2%. The fallibility of the generic ballot in presidential years, though, is clear in the chart below.2Galup data from 1988 was not available.3Data is based of ‘likely voters’ for 1976 and 1996-2006 and ‘registered voters’ otherwise4The two-party generic ballot was used when available (2004-2016)5Data from Real Clear Politics was rounded to nearest integer to make it consistent with Gallup’s data


Data: Gallup61968-2000, Real Clear Politics72004-2016

Since 1968, the generic ballot has missed the real House popular vote by an average of 4% and until 2008, it consistently overestimated Democratic support.  Both of these problems have been ameliorated in recent years, resulting in a more accurate and balanced  generic ballot since the late 1990s. And even though the generic ballot is less accurate in presidential years, it is still correlated with election results.8Data is based on the chart above. However, data from Real Clear Politics (2004-2016) is rounded to two decimal places rather than the nearest integer as in the chart

A party that performs better on the generic ballot will generally earn more votes in the election. The R2 in the bottom left corner indicates how much of the variance in the dependent variable (Democratic Margin in the Two-Party Vote) can be explained by variance in the independent variable (Democratic Margin in Generic Ballot). In English: R2 shows how well Variable 1 can explain or predict Variable 2. Here, R2 equals almost exactly 0.5, meaning that about half of the variance in the popular vote can be explained by the generic ballot.

Looking at the equation above the R2 value, the trend line has a slope of 0.54. This means that in general a 1% increase in a party’s margin in the generic ballot translates to about a 0.54 % bump in the House popular vote. There is still plenty of variation, though (see how the data points are not clustered too closely along the trend line), so this is not at all a perfect measure for any individual election. Even with this variation, and the knowledge that a lead in the generic ballot usually overestimates electoral success, a party is better off leading the generic ballot than trailing. And their better off leading with a larger margin than a smaller one.

Two caveats to this data. First, the makeup of the House of Representatives is not determined by the popular vote. Seat apportionment, gerrymandering, demographic & partisan sorting and other structural imbalances mean that a party’s share of the national House vote can differ substantially from the share of seats they actually win. Second, this data is from polls within a few days of the elections. We’re still a year and a half away from November 2020. The next two posts will focus on understanding these qualifications to the generic ballot.