The slide in NFL ratings could be as much a trend as a blip.

The presidential campaign, the growing move away from cable, the increase in live streaming sports and competition from compelling baseball have all been given as reasons for a double-digit decline in viewership through the first five weeks.

All legitimate explanations, experts say. But one of the main selling points of live sports to the networks — they’re appointment viewing that most people don’t like to record and watch later — could be eroding, as the fan base fragments, even for America’s most popular sport.

According to Sports Media Watch, viewership for last week’s games was down 26 percent for Monday night, 15 percent for Sunday night (against the second presidential debate) and 20 percent for Thursday night. Overall, for the first four weeks of the season, ratings across the league were down 11 percent.

The decline was concerning enough that league executives recently sent an internal memo to the NFL media committee, comparing this year’s slide to a lesser decline during the 2000 election cycle and conceding that, “While our partners, like us, would have liked to see higher ratings, they remain confident in the NFL and unconcerned about a long-term issue.”

The current TV contracts, worth between $8.5 billion to more than $15 billion each, expire in 2021 and 2022.