Third party voters are always what tip the election towards one party or another. Those swing voters decide who’s going to win battleground states, and the election. We decided to look at both the 2012 and 2016 elections to get a sense of just how important winning the swing votes could be to winning the 2020 election. We found the past election results for 14 battleground states in the current election: Arizona, Florida, Georgia, Iowa, Michigan, Minnesota, Nevada, New Hampshire, North Carolina, Ohio, Pennsylvania, Texas, Virginia, and Wisconsin.

Because we were looking for swing voters that would give the two major party candidates a win by majority vote, we couldn’t apply our model to the 2012 election since one of the major party candidates had already won each of the swing states by over 50%. The small number of swing voters there were wouldn’t have made a difference because of this. In 2016, however, there was an average of 4.13 times as many undecided voters in each swing state we looked at. For example, Minnesota had 8.7% of its actual voters not vote for Hillary Clinton or Donald Trump, while only 2.1% of Minnesota voters didn’t vote for a major candidate in 2012. This gives the swing voters the power to decide the election.

For each of our battleground states, we calculated what percentage of the undecided voters each major party candidate would’ve had to carry to win the state by a majority, rather than plurality, vote. For deciding the election, we assumed a uniform vote across states for undecided voters. This is an oversimplification, but allowed us to make observations about how these voters can swing an election. We determined what percentage of the swing votes Clinton or Trump would’ve needed to win each battleground state based on the election percentages. This was done with the formula (50-a)/s 100, where a is the actual vote for a candidate and s is the percentage of voters in the state that didn’t vote for either candidate. In some states, such as Ohio, a major party candidate won, making it impossible in our model for the other candidate to win.

Table 1: Left 2 columns: 2016 vote percentages for Clinton and Trump in the 14 2020 tossup states. Right two columns: % of remaining votes (third-party + write-in) that each candidate would have had to win to get a majority in each state. A negative % indicates that the candidate won a majority of the vote, while a % over 100 indicates that the other candidate won a majority of the vote.

According to our model, if Clinton had been able to swing Michigan, Wisconsin, and Pennsylvania, she would have gained 43 electoral votes and won the election. These were the states with the lowest percentages of third-party votes over 50% that Clinton would have had to win to get to 270 electoral votes. In states like Texas, Iowa, Georgia, and Ohio, Trump had the majority of votes, so the third party votes wouldn’t have made a difference. Clinton would have had to win all of the third party votes, in addition to votes that weren’t there. Given that she only needed to swing 58.1% of the undecided and third-party voters to her side to win the election, a number only 7% higher than her 2-party nationwide vote percentage, this goal was attainable. The election could’ve easily come down to the swing voters.

Third-party and undecided voters could easily decide the current election. In Georgia currently, Joe Biden is up by less than a point, with about 7% of the vote either undecided or third-party. That leaves 16 electoral votes in the air. In Ohio, which has 18 electoral votes, Trump is up 1.5 points, while there’s 5.6% undecided votes in the state. With 12 other states that could potentially go in either direction, having all voters vote for one of the two parties can easily decide the election. This election specifically, there has been a major push from both major parties to avoid voting for 3rd party candidates. 3rd party votes have been categorized as ‘throwaways’ with both Biden and Trump fighting to secure all of the votes they can. In key states like Georgia and Ohio, those 3rd party votes will decide for the entire voting population what direction the state goes, putting the burden on the undecided voters to name a winner this election cycle.

Table 2: Predicted votes in swing states and percentages of undecided + third party votes needed by each candidate to win each state. Bolded percentages are those below the 58.1% Hillary would have needed to swing the election in 2016.

Based on our calculations, it’s easy to see how important it is to vote for a major party candidate. Votes for third party candidates are indirectly votes for whichever candidate is behind going into the election, which can swing the election toward the candidate less favored. In 2016, third party votes swung the election towards Trump. In 2020, the same could happen, unless undecided voters vote for one of the two major party candidates.