Category Archives: US elections

Forecasts for the US Midterm Elections 2018

By Stephen Fisher.

The most striking thing about the forecasts for today’s midterm elections in the United States is that they have been much less talked of in the media than in previous campaigns. This is partly because in 2016 most of the forecasters put very high probabilities (90%+) on Hilary Clinton winning the presidency. (See here for a post-mortem.)

This post reviews the main statistical model based forecasts for the US House and Senate, with some discussion of the methodology and comparison with other forecasts. Overall, and as usual, there is not much variation between the forecasters in their central forecasts. They all point to the Democrats taking control of the house and the Republican retaining control of the Senate. The striking exception is a Gallup poll suggesting 50% think the Republicans will retain control of the House and only 44% think the Democrats will win it.

Despite the forecasts differing from the expectations of the American people, the forecasts appear to have been widely accepted in the media. So much so that some journalists suggest it will be a vindication of Donald Trump if Republicans maintain control of the House. However, if that happens it will most likely be despite a clear lead for the Democrats in the popular vote. In which case, it would be the electoral system, not Trump, that thwarts the Democrats. Meanwhile, if there are net Republican gains in the Senate it will be primarily because the Democrats are defending a big haul from 2012.

House forecasts

As James Campbell has noted, in all but three midterm elections since 1900 the President’s party has lost seats. Since 1950 the average loss has been 24 seats. The Democrats need to make net gains of 23 or more to take control.

Continue reading Forecasts for the US Midterm Elections 2018

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Why was Trump elected?

by Stephen Fisher.

This question can be addressed from various angles and at different levels. I will start with the basic features of the result, then discuss the patterns of change since 2012, all before trying to address the bewilderment of many who find it hard to understand how anyone could vote for him.

Trump won the presidency by holding on to states that Romney won and winning some states that Obama previously won, including Iowa, Florida, Ohio, Pennsylvania and Wisconsin. He did this by a combination of a national vote swing of around 1.5 points since 2012, plus above average swings in some key battleground states, such as Pennsylvania 3 points, Michigan 5 points and Iowa 10 points.*

At the same time, Trump lost the national popular vote but won the presidency by narrowly winning Michigan, Wisconsin, Pennsylvania and Florida with leads of less that 1.5 points each. So, had the swing to Trump in these states been smaller by just 1 point then Hilary Clinton would have won outright.  This was a close election. Continue reading Why was Trump elected?

What to make of the US election forecasts?

By Stephen Fisher

The majority of forecasts point to Hilary Clinton winning tomorrow’s US presidential election. Several of the poll, market and expert forecasts with probabilities for who will win are helpfully summarised by the New York Times here.  The polls-based predictions are all, apart from one, pretty confident that Clinton will win. At the time of writing, Drew Linzer’s model at Daily Kos puts the probability of a Clinton win at 87%, HuffPost has 98% and Sam Wang at the Princeton Election Consortium estimate is as high as 99%. The New York Times’ own model is slightly less confident, on 84%. The exception is Nate Silver’s FiveThirtyEight model which puts Clinton’s chances at just 67%.

The lower probability for Clinton in the FiveThirtyEight model is partly (by comparison with most but not all models) due to 538 having a smaller estimate of her likely lead in votes. By comparison with HuffPost, for instance, this is because FiveThirtyEight put more weight on more recent polls that haven’t been so great for Clinton in wake of the FBI announcement last week of further investigations into her emails.

But the discrepancy is mostly due to the FiveThirtyEight model allowing for more uncertainty. So 538 have a higher probability of a Clinton landslide than other models as well as a higher probability of a triumphant Trump. Continue reading What to make of the US election forecasts?

Republican seat gains in the House off a swing to Democrats since 2010?

by Stephen Fisher

There was clearly a swing to the Republicans since 2012 in yesterday’s US midterm elections. However, the most comparable recent election for the House contest was not the general election but the 2010 mid terms.

The Democrats seem to have recovered votes since the 2010 big wave Republican takeover. According to yesterday’s exit polls, there has been a small (1 %) swing to the Democrats. And yet, the number of Republican House seats has increased from 242 in 2010, to a likely (at the time of writing) final tally of around 248 this year. Continue reading Republican seat gains in the House off a swing to Democrats since 2010?

A guide to the US midterm election forecasts

Stephen Fisher and Jonathan Jones

Tomorrow Americans go to the polls for the midterm elections. All 435 seats in the House of Representatives are up for election, as well as 36 Senate seats and a host of state and local offices.

The historic tendency for the President’s party to lose ground in midterm elections, is sufficiently strong to say that there is virtually no chance of the Democrats regaining control of the House. Meanwhile the experience of previous midterm elections with a second-term President suggests that the Republicans should have a decent of winning the extra six seats they need to take control of the Senate.

Not only history but also political and economic circumstances in recent months, and especially current polls for individual Senate races suggest the Republicans have, according to the main forecasters, at least a two-thirds chance of achieving a Senate majority.

We are not attempting to forecast the outcomes of any of these elections, but several others with excellent track records for US election forecasting are. This article purely provides some introduction and links to the forecasts and offers some commentary from a British election forecasting perspective. We consider the House forecasts before turning to those for the Senate. Continue reading A guide to the US midterm election forecasts

US Elections 2012: Some initial thoughts on the results and polls

The big political story is no change. Obama is still the president, there looks like there will be very little change in the party composition of the Republican held House and Democrat led Senate. Given the polarisation of US parties at the moment, this seems to be a recipe for continued legislative gridlock. The last Congress was the least productive in over 120 years. Continue reading US Elections 2012: Some initial thoughts on the results and polls