Increasing partisanship, competing streaming options and the mostly virtual nature of this year's programming may help explain why TV ratings for both conventions were way down compared with 2016.

Why it matters: Ratings are not a proxy for popularity or voter enthusiasm, but they do provide a loose sense of which party and figures are capturing the attention of the country.

By the numbers: Viewership for the Republican National Convention was down about 21% on average this year across all four nights compared with 2016, per figures from Nielsen, while the Democratic National Convention's was down about 17%.

• The DNC averaged 21.57 million viewers in the 10 p.m. prime-time hour across the four nights that it aired last week, while the RNC averaged 18.8 million viewers over that period this week.
• President Trump's nomination acceptance speech at the White House on Thursday was watched by 23.8 million people, just shy of the 24.6 million people who tuned in for Joe Biden's speech the week before.

The numbers show how increasing partisanship in America may be curtailing viewership.

• The ratings drop for the RNC and the DNC were heaviest in viewership via traditional broadcast networks like CBS, NBC and ABC, compared to cable. Broadcast news networks tend to attract less partisan viewers than their cable counterparts.
• Fox News received the most total viewers among all networks, cable and broadcast, across all four days of the RNC, while MSNBC beat out all other broadcast and cable networks for every night of the DNC.

Between the lines: There's no way of measuring exactly how many people streamed the conventions or watched clips on social channels, but presumably, millions more Americans tuned in online via streaming and clips on social media.