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Midterm congressional elections: ET papers

The American Political Science Review (APSR), for its centennial, went through the citation counts for the thousands of articles it published in the last hundred years. For the 20 most-cited articles, the authors (or their surrogates) were asked to write an account of their citation classic.

Here then is my nostalgic account of another career and of "Determinants of the Outcomes of Midterm Congressional Elections," APSR, 69 (September 1975), 812-826. After that, the original article is reproduced, then followed by another APSR paper of mine, which I think is a stronger paper, although it ranked only in the all-time top 60 cited papers: "The Relationship Between Seats and Votes in Two-Party Systems," APSR, 67 (June 1973), 540-554.

-- Edward Tufte

Response to Midterm congressional elections: ET deja vu

Connoisseurs of statistical practice will enjoy, in the ZBAU graph, the heaping of t-values between 2.0 and 2.4, as regression coefficients stumble over the line to reach statistical significance (recall the rule of thumb about the sanctification value of t-values exceeding 2.0). This curious heaping suggests that scholars might have searched through many model specifications to root out what Bill Nordhaus, my colleague in economics, called the "Darwinian t-statistic," the selection of the fittest.

-- Edward Tufte

Here's the latest research on midterm congressional elections by two substantial scholars:

James E. Campbell (2006) "Forecasting the 2006 National Elections to the U.S. House of Representatives", The Forum: Vol. 4: No. 2, Article 2.

ABSTRACT: Drawing on several theories of congressional election change, this article presents a forecasting equation for seat change in U.S. House elections. The equation addresses the problem of the over time comparability of seat change when levels of competition at the congressional district level have declined dramatically, a decline that has substantially reduced the magnitude of net partisan seat change in recent decades. The equation is estimated using both on-year and midterm elections since 1944. It indicates that the 2006 midterm will likely be a good year for the Democrats. However, because of reduced levels of competition restricting the number of seats that are effectively "in play," Democratic Party gains are likely to be in the teens. Though Republicans may narrowly retain their control of the House, there is a very real possibility that Democrats will end the six election string of Republican House majorities.

Alan Abramowitz (2006) "Using the Generic Vote to Forecast the 2006 House and Senate Elections", The Forum: Vol. 4: No. 2, Article 3.

ABSTRACT: This article describes a model for forecasting the outcomes of congressional elections based on national political conditions and candidate behavior. Pre-election Gallup Poll data on the generic vote and presidential approval are used to measure national political conditions and data on open seats and challenger quality are used to measure the behavior of congressional candidates. The model is tested with data on U.S. House elections between 1946 and 2004. A simpler model based only on national political conditions is tested with data on U.S. Senate elections from the same period. The results indicate that Democrats have a good chance to regain control of the House of Representatives in November. Democratic gains are also likely in the Senate but it will be difficult for Democrats to pick up the six seats that they need to take control of the upper chamber because only 15 of the 33 seats up for election in 2006 are currently held by Republicans.

-- Edward Tufte

A major analytical issue in recent elections is the apparent loosening of the link between economic prosperity and support for the white house party. The presidential election models based entirely on economic conditions predicted a Gore landslide in 2000, for example.

In the current midterm congressional election, why is it that the current prosperity (benefiting the Republicans) seemes to be swamped by other factors? One way to answer that question is that the Republicans would be even worse off if the economy were in recession.

But there is something of a historical decoupling. Why?

Favorable macroeconomic conditions prevailing in election years might help the incumbent party less than in the past because the benefits of good times now go largely to the top 10% or 20% of the overall income distribution. Thus prosperity that is not widely distributed fails to turn directly into votes, although it may turn into campaign contributions induced by tax cuts.

In short, the story in the past was that a rising tide raises all boats; nowadays a rising tide raises all yachts.

-- Edward Tufte

A report uses the yacht quote: ``The story used to be a rising tide raises all boats, and now it just raises all yachts,'' says Edward Tufte, a political scientist at Yale University in New Haven, Connecticut. ``The benefits of a good economy are much more narrowly focused now on the top 20 percent.''

"Bush, Republicans Find Strong Economy Doesn't Win Middle Class," by Brendan Murray here

-- Edward Tufte

Most of the news forecasts for the House predict a 15-20 seat Democratic gain. These forecasts are based on district-by-district analysis in what are judged the most competitive seats (only about 8% to 10% of the 435 House elections).

This is probably an undersample of the number of Republican seats actually in play. In turn, my guess is that this is an underestimate of the seat-change because the turnover rate is an esculating function of the size of the swing toward the Democrats; the larger the swing, the disproportionately larger the turnover in seats.That's because there are very few really competitive seats (where the district is divided, say 52-48, for either side), but once the swing toward the Democrats exceeds 3% or 4%, then a lot more Republican seats come into play.

So I'll say >30 seats gained by the Democrats, which should be discounted by the unknown Republican turnout effects, by a November surprise, and by my enthusiasms. So an interval forecast would be 25 to 35.

This is from someone who, years ago as a consultant to the New York Times, helped to elect Elizabeth Holtzman to the US senate in 1980 on the first edition of the front page of the New York Times on election night. By the next day, Al D'Amato was elected senator in a very close vote. This one of my two errors in helping to forecast probably a hundred races on election night for in various elections over the years for NBC, Newsweek, CBS, and The New York Times. As I recall, we had an apparently somewhat solid exit poll (which I had not looked at in detail or with my usual skepticism) and some gossip that ABC had it for Holtzman. I wrote a note to myself afterwards about the importance of always going off quietly, away from the hectic newsroom, and looking at the data, saying what I saw in the data, and letting the editors and writers handle all gossip input. Calling the races on election night is part of a bureaucracy so there were other people who participated in the mistake.

My other error was at CBS. I was working for Bill Moyers and his writers, analyzing a midterm election, and made a prediction that was broadcast fairly early on election night. I substantially over-estimated the House shift toward the Democrats (probably by 8-10 seats, it turned out). This number, when broadcast, prompted an immediate phone call from an outraged well-known Republican honcho who denounced the prediction, correctly as we found out by the end of the evening. My error was to over-estimate the swing ratio (the national swing in seats resulting from the national swing in votes for Congress). I am using this same methodology for 2006, except without any real data this time. On Wednesday morning, however, the swing ratio for 2006 will have been exactly calculated..

-- Edward Tufte

This morning, after the election, the House of Representatives looks like 28 to 33 seats Democratic swing, which is agreeable with the October 31, 2006 forecast above. My forecast was more than 30 seats, with an interval of 25 to 35.

There are still several uncertain seats that, if they break equally, take the result to the high side of the interval. Early Wednesday morning, MSNBC says 33 based on all 435 seats. The New York Times has "at least 27" with some undecided. The Washington Post has 27 on 423 seats called and 12 undecided (by the Post at least). Splitting the 12 equally yields a swing of 33. Chris Cillizza of the Post, in his interesting weblog, had it at 30 shortly after midnight.

So on the morning after the election, the cloud of uncertainty been reduced from the forecast uncertainty of +/-5 seats to the election uncertainty of +/-3 seats!

-- Edward Tufte

Today's press conference, George W. Bush: "The amazing thing about this election, and what surprised me somewhat, which goes to show I should not try punditry, is that this economy's strong. And, a lot of times, off years are decided by the economy."

As discussed above, the apparent delinkage of economic prosperity with support for the White House party is possibly the result of the changed distribution of prosperity beginning in the 1980s (the Rising Yachts Theory).

The other variable in the model is presidential approval rating in the pre-election run-up (Bush's approval rating was the second lowest in the 16 midterms since 1946) data here.

Also some 5-10 House seats were lost by the White House party because of local district scandals. It is difficult to model, over a series of midterm elections, the sometimes very powerful effects of election-unique or district-unique variables such as Iraq, corruption, differential turnout, and so on. Sometimes after-the-fact dummy variables are added to the fitted equations to account for a special factor in a single election (and possibly to get better estimates of the coefficients on the more general variables in the model), a technique which never appealed to me despite its boost in R-squared.

-- Edward Tufte

Response to Midterm congressional elections: ET deja vu and thoughts about 2006

Additional discussion about the designs used to report the 2006 election on the thread Mapping election results.

-- Niels Olson (email)

Insider projections, apparently real not just for pitching (from Newsweek):

"Rove's miscalculations began well before election night. The polls and pundits pointed to a Democratic sweep, but Rove dismissed them all. In public, he predicted outright victory, flashing the V sign to reporters flying on Air Force One. He wasn't just trying to psych out the media and the opposition. He believed his "metrics" were far superior to plain old polls. Two weeks before the elections, Rove showed NEWSWEEK his magic numbers: a series of graphs and bar charts that tallied early voting and voter outreach. Both were running far higher than in 2004. In fact, Rove thought the polls were obsolete because they relied on home telephones in an age of do-not-call lists and cell phones. Based on his models, he forecast a loss of 12 to 14 seats in the House--enough to hang on to the majority. Rove placed so much faith in his figures that, after the elections, he planned to convene a panel of Republican political scientists--to study just how wrong the polls were. . . .

The numbers looked a lot less rosy to the other architect of the campaign--RNC Chairman Ken Mehlman. It was Mehlman who built the much-vaunted turnout machine. But he feared that many inside the party were relying too much on technology, like voter databases, and had lost sight of the bigger picture: that voters were turning against them. "We've built a great new car, but the gasoline for the car isn't us; it's the candidates and the issues," Mehlman told NEWSWEEK. There was no bigger issue than the war, which Rove had pushed as a winning theme for the GOP. As he flew back to D.C. on a private jet two days before the elections, Mehlman scribbled his predictions on a card--not to be revealed until after the elections. His numbers were much closer than Rove's: the GOP would lose 23 in the House (5 short of the final tally), 5 in the Senate (1 shy) and 6 governors (spot on). Last week Mehlman announced he would step down and pursue opportunities in the private sector."

-- Edward Tufte

Bush radio address this weekend: "One freedom that defines our way of life is the freedom to choose our leaders at the ballot box. We saw that freedom earlier this week, when millions of Americans went to the polls to cast their votes for a new Congress. Whatever your opinion of the outcome, all Americans can take pride in the example our democracy sets for the world by holding elections even in a time of war."

Lucky us.

-- Edward Tufte

A big list of election predictions (many of them wishful thinking) at

Looks like Larry Sabato of the University of Virginia nailed it.

-- Edward Tufte

According to Chris Cillizza of the Washington Post, the current midterm result is a swing of 29 to the Democrats, with 5 seats still undecided. For various reasons, none of the 5 are likely to change the swing of 29.

My forecast last October was a swing >30, with a range of 25 to 35.

Cillizza, by the way, provides a list of the 10 seats most likely to switch parties in 2008! (posting of December 1, 2006).

-- Edward Tufte

With a surprise result yesterday in a Texas run-off, it is now 30 seats as the swing toward the Democrats in the House! There is still one contested seat, which will probably go Republican.

-- Edward Tufte

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