Ganassi's Scott Pruett and Memo Rojas withstood near-relentless pressure to win the Long Beach United SportsCar round.
Rojas stayed at the head of a four-car lead train through the first stint, as the Action Express and Wayne Taylor Racing Corvette DPs and the OAK Morgan-Nissan battled on the Ganassi Riley-Ford's tail.
Action Express managed to get Joao Barbosa into the lead during the sole pitstop sequence, but Pruett snatched first place back on track, with Jordan Taylor slipping through into second at the same time.
After a spell in which Taylor and Barbosa were too busy with each other, Pruett was reeled in again and took the chequered flag just 0.7 seconds clear of the Taylor brothers' car.
Barbosa and Christian Fittipaldi completed a close top three for Action Express, while OAK's Olivier Pla and Gustavo Yacaman were the top LMP2 crew in fourth.
The front-row starting Michael Shank Racing Riley-Ford was squeezed into the tyres at the first corner, then ended up in the wall again later on when Michael Valiante spun in John Pew's path.
Antonio Garcia and Jan Magnussen dominated GTLM - the only other class present as Long Beach is among the rounds not attended by all four divisions - for Corvette.
Garcia established a comfortable advantage during his stint, with Magnussen praising his team-mate for giving him a relative easy run to the flag.
Corvette only just missed out on a one-two, as RLL BMW's Dirk Muller held off Tommy Milner for second.
The Bill Auberlen/Andy Priaulx BMW had been on course for a class podium before the need to change a door slowed its pitstop, leaving it sixth at the finish behind the CORE Autosport Porsches.
Leading results - 77 laps:
Pos Cl Drivers Team/Car Time/Gap
1. P Pruett/Rojas Ganassi Riley-Ford 1h40m46.184s
2. P Taylor/Taylor Taylor Corvette DP +0.759s
3. P Barbosa/Fittipaldi Action Express Corvette DP +4.251s
4. P Pla/Yacaman OAK Morgan-Nissan +29.247s
5. P Westbrook/Valiante Spirit Corvette DP +1m19.445s
6. P Sharp/Dalziel Extreme Speed HPD +1 lap
7. P Brown/van Overbeek Extreme Speed HPD +1 lap
8. GTLM Magnussen/Garcia Corvette +2 laps
9. GTLM Muller/Edwards RLL BMW +2 laps
10. GTLM Gavin/Milner Corvette +2 laps