Richard Westbrook enjoyed a slender lead aboard the #5 JDC Cadillac DPi-V.R over the #48 Action Express-run Ally Racing Cadillac of Mike Rockenfeller at the 12-hour mark just after the 11th full-course yellow period of the race.
That followed an eventful couple of hours in which the overall lead changed hands multiple times amid a succession of caution periods.
The erstwhile-leading #02 Chip Ganassi Cadillac was the first DPi runner to hit trouble when Alex Lynn picked up a puncture and then a penalty for not controlling the restart properly after the seventh full-course yellow period.
That left Ricky Taylor at the head of the field in the WTR Acura ahead of the similar Meyer Shank machine of Tom Blomqvist, with Taylor handing off to Rossi during a green-flag pitstop shortly before the eighth FCY.
At the restart, Blomqvist grabbed the advantage with a brave move on Rossi at the recently-renamed Le Mans chicane, although MSR lost out at the next round of stops when Helio Castroneves took over the #60 Acura from Blomqvist.
Castroneves regained the initiative during the next round of stops at the following FCY period, running second behind the off-strategy #31 Action Express Racing Cadillac of Tristan Nunez and then taking the lead when Nunez stopped just after the 10th FCY period.
The succession of cautions allowed the #2 Cadillac, now in the hands of Earl Bamber, to get back on the lead lap, and the Ganassi machine soon emerged as the MSR Acura’s strongest challenger as Bamber scythed his way up the order.
Bamber managed to pass Castroneves to take the lead midway through the 12th hour, but lost the advantage when he pitted to hand over to Marcus Ericsson at the next round of stops, with Castroneves staying aboard the #60 car.
Both cars were then hit with penalties – Castroneves for pitlane speeding, and Ericsson for making contact with the AXR car of Nunez, which delayed both the #02 and #31 Cadillacs.
That temporarily put the #10 WTR car of Rossi back into the lead, but both Westbrook in the JDC-Miller Cadillac and Rockenfeller in the #48 Ally machine stayed out as the remainder of the DPi pitted under the subsequent FCY period.
The race restarted just before the 12-hour mark with Westbrook heading Rockenfeller, Castroneves and Sebastien Bourdais in the #01 Ganassi Cadillac. Filipe Albuquerque was fifth in the #10 WTR Acura ahead of Ericsson and the #31 AXR Cadillac, now in the hands of Mike Conway.
LMP2: PR1/Mathiasen heads tight battle
In LMP2, the #52 PR1/Mathiasen Motorsports Oreca led the way by virtue of staying out at the previous caution period, with Mikkel Jensen holding a slender lead over the #29 Racing Team Nederland machine of Rinus VeeKay.
IndyCar star Pato O’Ward survived an off on his out lap to run third in the DragonSpeed Oreca, ahead of the Luca Ghiotto in the best of the G-Drive Racing by APR cars and Louis Deletraz for Tower Motorsports.
High Class Racing fell out of contention when Fabio Scherer suffered a major off at Turn 1, albeit the Swiss driver managed to coax the heavily-damaged #20 Oreca back to the pits.
There was also drama for the #11 PR1/Mathiasen entry, which went behind the wall during Steven Thomas's stint and now runs some 11 laps down.
In LMP3, Riley Motorsport enjoyed a comfortable lead with Kay van Berlo aboard the #74 Ligier, with only one other car in the class, the #13 AWA Duqueine, still on the lead lap at the halfway mark.
GTD Pro: WeatherTech Mercedes hits the front
WeatherTech Racing seized the advantage in GT Daytona Pro as Maro Engel in the #97 Mercedes-AMG GT3 passed the KCMG Porsche 911 GT3 R of Alexandre Imperatori just after the restart following the 11th FCY period.
The Risi Competizione Ferrari 488 GT3 had built up a cushion out front in the hands of Alessandro Pier Guidi, but this was negated when the team chose to complete a brake change under an earlier caution.
Pier Guidi escaped with a warning when he made contact with the GTD-class leading #32 Gilbert Korthoff Mercedes of Mike Skeen, with teammate James Calado running third at the halfway mark.
Dirk Muller had the #15 Proton Competition Mercedes in fourth place ahead of the TR3 Racing Lamborghini Huracan GT3 of Andrea Caldarelli.
Both Corvette C8.Rs are now out of contention, with the #3 car running 13 laps down following its alternator issue.
The lead also changed hands in GTD shortly after the most recent caution, as Ollie Millroy in the #70 Inception Racing McLaren 720S passed Richard Lietz in the #16 Wright Motorsports Porsche 911 GT3 R.
The #32 Mercedes ran third in the hands of Stevan McAleer following Skeen’s earlier off before being passed by Marc Miller's Gradient Racing Acura NSX GT3 and the Magnus Racing Aston Martin Vantage GT3 of Andy Lally.
