From article:

Our team created email addresses with different email providers and signed up for the email lists of around fifty different candidates, committees, and political nonprofits. In the month leading up to the election, we tracked how many emails were sent from each entity, and what percentage of those emails made it into our inbox.

In Nevada, Democrat Jacky Rosen averaged over 90% placement in inboxes, compared to Dean Heller’s over 90% placement in spam.

In Florida, 100% of Republican Rick Scott’s emails went to spam in Yahoo, while 100% of Bill Nelson’s emails went to our Yahoo inbox.

While these were the most dramatic examples, this pattern emerged in every toss-up Senate race we tracked.