Three decades after its original GTP series went bust, IMSA’s WeatherTech Championship is booming according to crowds and TV ratings. But how will the series’ popularity hold up in the face of a possible decline in car count next year for the premier GTP class, where the grid for sprint races is already down to eleven cars?Part of the answer may lie in social media.At Long Beach, it became clear that Acura and it’s two-car entry would not return for the 2027 season, which could leave just four manufacturers in GTP. Acura is headed to the exit after parent company Honda’s $2.7 billion loss in its last fiscal year. Also troubling, Genesis Magma Racing, McLaren Racing, and Ford Racing, which are committed to the World Endurance Championship, have recently begun hedging on when—or if, in the case of Ford—their new prototypes might also join IMSA’s GTP ranks.There is some good news. In addition to record ticket sales at major endurance races, there’s been a big boom of online followers of the WeatherTech Championship on YouTube. IMSA’s position is the more the merrier when it comes to influencing manufacturer participation. But its growing attendance numbers can be a little fuzzy. The announced record crowds for this year’s Rolex 24 at Daytona and the Mobil 1 Twelve Hours at Sebring, for example, cited multi-day attendance, which counts the same fans several times. We estimate the record race weekend crowd at Daytona to have been 45,000 to 50,000, and the record race day crowd at Sebring to have been 60,000 to 65,000. IMSA WeatherTech SportsCar Championship Rolex 24 at DaytonaThe biggest jump in numbers comes on social media. IMSA’s official YouTube channel now has 1.74 million subscribers after a concerted effort to go after a broader target online. That effort has resulted in more followers on YouTube for IMSA than NASCAR’s 1.7 million and the 481,000 for the NTT IndyCar Series. These numbers can be a little fuzzy, too, because NASCAR and IndyCar fans enjoy broad access to races via broadcasts and cable programming on linear TV. That generates more live (or replay) viewership and less demand for online content. In the WeatherTech championship, NBC has only 17 hours of broadcast coverage, including Long Beach and the upcoming Chevrolet Detroit Sports Car Classic on May 29. The majority of NBC’s coverage is on the Peacock channel. It currently has 46 million total subscribers via cable networks or streaming, less than half the 128 million homes reached by broadcast TV. For those who cannot bring themselves to get over the hurdle of a streaming fee at Peacock, IMSA is very aggressive about sharing video content online during races. But the biggest single driver on YouTube is the live streaming internationally of all of NBC’s telecasts on IMSA’s official channel—which gets geo-blocked inside the US. After initial unannounced experiments in 2024, availability of live races on IMSA’s official YouTube channel outside the US began in earnest in 2025. The online numbers and growth are impressive as is the skew toward a younger demographic. This year’s Rolex 24, for example, had “Peak Concurrent” viewership of 209,000. That’s a huge jump from 72,000 last year. For the entire 24-hour, YouTube participation reached 1.6 million.This, too, is a bit of a cautionary tale. YouTube does not have the technology to determine the number of unique users. Total viewership no doubt includes the same “comers and goers” for the endurance races. And, by contrast, even the total participation number for the recent dramatic WeatherTech Championship sprint race at Laguna Seca won by the privateer Porsche 963 of JDC-Miller Motorsports was 233,000, significantly lower than Daytona’s total. (The Peak Concurrent numbers, invariably far lower than the overall figure, are not available for the Laguna race.)The contract for IMSA coverage by NBC is in the second year of a seven-year deal. The number of unique Peacock viewers during this year’s Rolex was 784,000, which more than doubled the figures in 2025. Meanwhile, the broadcast coverage on NBC of the start and finish reached a peak of 1.1 million. Elsewhere online, IMSA’s special “Win the Weekend” series and the “IMSA Endurance Hour” are gaining footholds. IMSA claims a total footprint of 4 million with its social media.IMSA WeatherTech SportsCar Championship Mobil 1 Twelve Hours of SebringIt remains to be seen how soon Genesis, which is already earning championship points after just two races in the WEC, and McLaren, which will not join the WEC and its Hypercar category until next year, choose to move into the GTP ranks. Cyril Abiteboul, manager of the Genesis program, cited a WEC schedule upset by the war in the Middle East as a possible cause for delay in its GTP plans. Zak Brown, McLaren’s CEO, cited high costs for hedging the company’s bet. Ford may skip GTP and decide to cast its entire lot in the WeatherTech Series with its already established Mustang GT3 program, according to Mark Rushbrook, Ford Racing’s director. As with all the manufacturers of the prototypes in Hypercar and GTP, an evolving rulebook that continues to hold down costs is the key concern.In any event, IMSA has found a unique approach to sustaining its appeal to manufacturers looking for fan followings in the expensive GTP class, which can only help avoid the peaks and valleys of the past.