Predicting Elections

adapted and updated from a feature on ABC News’ Nightline.

In 2012 Barack Obama and Mitt Romney ran for President.

All the TV networks and both campaigns knew by 3pm Central Time that Obama had won the election.

In 2008 Barack Obama and Bill Clinton and John McCain ran for President.

All the TV networks and both campaigns knew by 11:00am Central Time that Obama had won the election.

In 2004 George W. Bush ran against John Kerry for President.

All the TV networks and both campaigns knew by 4:00pm Central Time that Bush had won the election.

In 1996 Bill Clinton and Bob Dole ran for President.

All the TV networks and both campaigns knew by noon Central Time that Clinton had won the election.

In every election, the networks wait to broadcast this information until 8pm Central Time, when polls in the majority of states have closed.

In every election since 1964—except for 2000—the networks knew the outcome before the time the evening news was broadcast.

Why is it that TV networks are almost always right when they predict elections?

1. They are careful to take a large, good sample

In most election years, the networks pool

their resources to take a stratified random sample of as many

as 10,000 voters.

After the problems in 2000, they have surveyed 40 – 50,000 people each election.

2. They repeatedly poll each state before the election, looking for consistency in the results. They use the results to pre-sort states by how they expect them to vote (red vs. blue).

Pre-sorting lets them put most resources into “toss-up” states (like Iowa) that could go either way.

3. They compute an estimate of each candidate’s percentage of the vote, including a margin of error, and only call states where the victory margin victory exceeds the margin of error.

EXAMPLE Poll says the Republican

will win South Dakota with 58% + 3%

The Republican will probably get somewhere between 55% and 61%

Call South Dakota for the Republican.

EXAMPLE Poll says Democrat will win

Nevada with 51% + 3% The Democrat could get

anywhere between 48% and 54%

Nevada is too close to call.

4. The mathematics of statistics gives them confidence that their results will be correct between 95 and 99% of the time.

… So what went wrong in Florida in 2000?

The polls from all news agencies showed that the Florida race (and the nationwide electoral vote) was too close to call—which was, in fact true.

Most polls said Al Gore had won Florida, but by a smaller margin of victory than the margin of error for the poll.

ABC and CBS said later they felt pressure from advertisers to make a decision, so they called Florida for Gore around 9pm.

Fox News called Florida for Bush around midnight. (Later analysis showed Fox’s poll was also too close to call.)

After the Fox call, ABC and CBS took back their call for Gore and declared Florida too close to call.

Later reviews of the polls showed the ABC/CBS poll (which was also used by NBC and CNN) had a higher percentage of minorities than had actually voted in Florida.

The Fox poll had a disproportionately high percentage of voters in the northern part of the state, which went heavily for Bush.

Several independent investigations in 2001 and 2002 had mixed results.

Using a variety of re-count procedures, four investigations showed Gore would have won Florida, while three showed Bush would have won the state.

However the Supreme Court stopped the re-count, and Gore conceded the election long before these investigations happened.

… So, basically the networks were right. They just too quick on the draw. 

… It really was too close to call.