Daytona 500 television ratings took another plunge. (Sean Gardner/Getty Images)

Declining television ratings have been a near-constant part of the NASCAR conversation for years. Based on the overnight rating for the circuit’s marquee event, that chatter won’t be ending anytime soon. Sunday’s Daytona 500 drew a 5.1 overnight rating on Fox, which Sports Business Daily’s Austin Karp reports is likely a record low. It’s down 22 percent from the overnight rating scored by the 2017 edition, down 16 percent from 2016 and down 30 percent from 2015.

Karp points out that the Olympics probably cannot be used as an excuse here, considering the race fared better the previous time it went up against the Winter Games.

Overnight ratings measure television viewership in Nielsen’s top 56 metered markets, covering around 70 percent of U.S. television households, and provide an early indication of what the final TV ratings will be. They usually don’t fall far from the final ratings: Last year’s Daytona 500 scored a 6.5 overnight rating and a 6.6 final rating, which tied the 2016 edition as the second-least-watched Daytona 500 of all time, behind only the 5.6 in 2014 (when the race was delayed 6 hours 22 minutes by rain, pushing it up against NBC’s coverage of the Olympic’s Closing Ceremonies).

Early this century, NASCAR was seen as a ratings juggernaut: The 2006 Daytona 500 drew an 11.3 rating and 19.335 million viewers for NBC. But television viewers have fled the sport over the past decade — The Post’s Liz Clarke has been writing about the circuit’s faltering ratings since at least 2009 — with last year’s edition seeing a 42 percent ratings decline and a 38 percent decline in total viewers from 2006.

“To put the numbers in perspective, three years ago the Atlanta 500 — not exactly on the level of Daytona — pulled a 5.1 overnight,” Sports Media Watch reported Monday.

More perspective: Sunday night’s NBA All-Star Game also drew a 5.1 overnight rating on TNT and TBS. Sports Media Watch reports the Daytona 500 previously would draw much higher ratings than the NBA All-Star Game when they occurred on the same day. Not so much any more.

Reasons for NASCAR’s drop vary beyond the fact that fewer people are watching network television thanks to cord-cutting. A number of big-name veteran drivers — Dale Earnhardt Jr., Tony Stewart, Jeff Gordon, Matt Kenseth, Danica Patrick and Carl Edwards — have either retired or been pushed out by their teams, and their younger replacements have yet to garner an equivalently ardent level of support. Plus, fan support of NASCAR’s new stage-racing format, instituted last season, appears to be tepid at best.

Unlike the NFL, which also has seen a decline in television ratings, NASCAR cannot point to protests during the national anthem as a reason for its drop. Stock-car drivers and teams have rallied around the anthem as a sign of their all-American bona fides, drawing praise from President Trump, in stark contrast to the scorn he has directed toward protesting professional football players.

Trump tweeted his support of the race — and of NASCAR chief executive Brian France, a noted Trump supporter — before Sunday’s race:

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