Interest in the league, as measured by word-of-mouth company Engagement Labs, sank 26% since last season -- to 294 million impressions from 396 million the season before.
Engagement Labs' word-of-mouth data includes all consumer conversations -- person-to-person conversations as well as from social media.
The company said that 2016 had the lowest fan engagement since the company began tracking the NFL. In recent years, high word-of-mouth activity came in the 2011 season (618 million impressions) and the 2014 season (517 million impressions).
All this data has arrived as the NFL's total viewership regular-season TV ratings sank 8% to around 16.5 million Nielsen viewers per game on average.
Looking at specific data, word-of-mouth activity among teens was down a big 44%, and women were down 32% -- far more than men.
Engagement Labs reasons that some of this decline was due to the political season. Among those who identified themselves as Democrats, word-of-mouth conversations were down 11%. Independents had a steeper drop, at 42%. Republicans' word-of-mouth activity was up 2% since last season.