LatestPollResults.com has presented an unbiased probability analysis of the Electoral College for each Presidential elections beginning with the Bush/Gore contest in 2000. By analyzing the latest poll in each race, our poll-based analysis determines the race probabilities for each party's candidate. Using the race probabilities, we calculate the overall probability of winning by evaluating every possible outcome. In 2010, we extended our poll-based analysis to analyze the Senate races and compute the odds for each party to control the Senate. In 2016, we added our market-based analysis for the Presidential and Senate races, utilizing the pricing of futures contracts traded at the PredictIt.org marketplace. In 2018, we added our analyst-based analysis for the Senate and the House by analyzing the historical accuracy of the experts who provide qualitative ratings for every seat in the Senate and the House.
Our model has been consistent through the years. For the Presidential election, we determine the probability for the Democrat and the Republican candidate in each state, the District of Columbia, the two Maine districts and the three Nebraska districts which all have Electoral Votes. Each of these 56 different ways for a Presidential candidate to be awarded Electoral Votes, has an Electoral Vote value and a corresponding probability of occurrence. For the Senate, we determine the probability for each party's candidate in each of the Senate races, and for the House in each of the 435 House races. From these probabilities, we calculate the exact probability of winning for each party evaluating all possible outcomes.
Mathematically, it's challenging to calculate every possible outcome in a Presidential, Senate or House election from the individual state/seat probabilities. Most election-analysis websites opt to run tens or hundreds of thousands of election "simulations" in an attempt to estimate each party's overall probability of winning - the Presidency, or controlling the Senate or the House. Instead of estimating the overall probability with simulations, The Wizard of Odds ℠ probability model calculates the exact probability of every possible Electoral Value or seat distribution from which we calculate the overall probability of winning for each party.
Senate Election - Similarly, in analyzing the Senate, we calculate the probabilities for each Senate race, and use them to compute the probability of every possible seat distribution to obtain each party's overall odds of controlling the Senate. In a 50-50 Senate, the Vice- President casts the tie-breaker, thus the odds of a 50-50 tie are prorated according to the odds for each party to win the Presidency. In 2022, 35 Senate seats will be decided resulting in 2^35 or over 34 billion possible outcomes.
House Election - For the House, using the probabilities for the House races in each district, we compute the probability of every possible seat distribution to obtain each party's odds of controlling the House. With 2^435 possible outcomes, there are over 88 duoquadragintillion outcomes. This number is 131 digits long!
To determine the individual state/seat race probabilities, we use three distinct methods:
Our poll-based method is statistically-based probability analysis. We use the latest poll from each state/seat race to evaluate the probability of winning for the Democrat and the Republican. The probability is derived from the poll percentages for each candidate and the sample size of the poll. Once we have the individual probabilities for each state/seat race, we analyze all possible outcomes. Our poll-based method has a perfect record projecting the winner for the Presidency and the party to control the Senate:
In 2016, we began tracking and analyzing an alternate set of probabilities for the Presidential and Senate races. PredictIt.org has emerged as the leading prediction marketplace for real-money politically-based contracts.
Each contract trades in cent intervals between 1 cent and 99 cents and has a specific expiration date. Traders can buy or sell at the market price, any time until the contract expires. At expiration, the value of the contract will be settled at $1.00 if the event occurs and $0.00 if it doesn't. If the transaction is profitable, PredictIt deducts a 10% commission from your winnings. From the contract pricing, we derive the implied market-based probability for each candidate. For example, assume that a trader purchases a contract for the Democrat to win in Georgia and pays 60 cents for the contract. If the Democrat loses Georgia, the value of the contract will be $0.00 and the trader will have lost 60 cents. If the Democrat wins Georgia, the contract will settle at $1.00 and the trader will win 40 cents per contract, less 4 cents for the 10% commission. The net winnings will be 36 cents. The implied market-based probability of risking 60 cents to win 36 cents is 62.5%.
Based on the bid/ask prices for futures contracts trading on the PredictIt.org marketplace, we calculate the implied probability for the Democratic or Republican candidate in each state/seat race. Since trading occurs 24/7, these market-based probabilities offer a live snapshot of each race. Note, there is a contract for who will win the Presidency, which party will win control of the Senate, and which party will win control of the House. Several websites report the market odds for this contract. However, we compute the overall probability of winning from every possible outcome using the underlying individual state/seat race probabilities.
In 2016, the market-based model for both the President and Senate strongly pointed to a Clinton victory and a Democratic Senate. Entering election day, the market-based odds indicated Clinton's odds of winning were 87.6% while the odds that the Democrats would control the Senate were 65.8%. These market-based projections conflicted with our poll-based projections and proved to be inaccurate. Our poll-based and market-based projections both pointed to a Republican-controlled Senate in 2018 and in 2020, to a Biden victory and a Democrat-controlled Senate. and in
Since 2018, we've analyzed the major political analysts who provide a qualitative rating for every seat in both the Senate and House. The Cook Political Report, Inside Elections, Sabato's Crystal Ball, and Real Clear Politics are well known, widely respected, and have published their ratings in each of the last 5 election cycles. Seats are rated either Safe, Likely, Lean, or Tilt (Inside Elections only) for the Democrat or for the Republican or as a Toss Up.
Using our probability model, we assign a probability to each seat's rating based on the historical accuracy of the rating. From these individual seat probabilities, for each analyst, we analyze all possible outcomes and calculate the overall probability of winning for each party.
LatestPollResults.com is operated and co-authored by Stephen and Mark Delano.