The following is a statistical analysis of political data in the state of Michigan.
In 2024, in October, one could have compared existing poll data for Harris against polling data for Biden in 2020 & seen that she was under polling in battleground states like Michigan and was likely to lose. We can use the same method here to make a prediction about the senate race in 2026.
Let’s start by looking at overall trends. The following is a graph of Presidential Election results since 1992. While not conclusive, the key takeaway is the generally rising share of the Republican vote vs the stable Democratic share. The reason there seems to be a large gap in getting to 100% of the vote in the 90’s was Ross Perot as an independent candidate.
This graph below is the Senate share of the vote since 1992. The most obvious & surprisingly clean trend is closing of the share towards 50% from 2008. During the similar off year election in Trump’s 1st term, 2018, the Democratic candidate won by 275,660 votes. In 2024 the difference was 19,006.
The following graphs are the polling results vs. the actual election results for both President & the Senate. Since 2006 Democrats have reliably outperformed polls in both areas. This changes in 2016 where the Republicans outperform the polls for both the Senate & the Presidency. Moreover, the polling matches the trend seen earlier for Senate elections with the results showing a narrowing gap between Republicans & Democrats.
If 2018 is a good year to compare to because it occurred during Trump’s term & it is an off year election, we should expect Republicans to outperform polling averages by 1.8%.