As had been the case in final qualifying, the precipitation fell on only half of the track, causing umbrellas to go up in the vicinity of the pits but leaving the rest of the circuit unaffected. Almost immediately, the unpredictable conditions began to catch drivers out and, while local favourite Alex Tagliani escaped from a quick rotation after catching a damp kerb, the charging Heylen was not so lucky, clouting the wall and damaging the right rear corner of the Conquest entry.
Recovery of the #34 machine brought out the second safety car of the race, prompting Tracy to dive in for another splash of fuel. The majority of the field opted to stay out, however, figuring it wouldn't be long before the race went green and that they still had some laps in the banks thanks to the two reduced pace periods.
The conditions, though, remained tricky and, with the safety car still on track, Bourdais dropped the ball. Typically, the Frenchman was able to get off lightly, the #1 car bouncing through the gravel trap at the final corner before rejoining down in eleventh place, Doornbos now promoted to the lead. At the same time, however, Tracy's car quit under him, the engine smoking visibly, and the full course caution was extended, with Bourdais taking the opportunity to pit for the first time.
Europeans dominated the front of the pack when the race returned to green, with Doornbos heading Wilson, Clarke and Jani before Graham Rahal upheld home-grown honours, but the overseas contingent was to be reduced by one within five laps of the restart as Clarke slowed dramatically. The Briton wasn't even able to get his car back to the Minardi Team USA pit, pulling off at turn six to lick his wounds after another unfortunate exit while well placed.
Ironically, it was only another lap or so before the pace was reduced again, this time for the first of three on-course stoppages for Alex Figge. The field circulated in one long line while the rookie was towed to pit-lane, giving the leaders chance to make a dive for fuel and tyres, promoting Rahal to the lead.
With the sun making a welcome re-appearance overhead, slicks were again the order of the day, but the weather gods continued to play tricks, with the next shower just a couple of laps away. This time, Power was the one to be caught out, spinning at turn five, but the conditions also provided some close racing for the enthusiastic crowd as Pagenaud dived down the inside of Wilson, only to see the Briton fight back further around the lap. Indeed, Wilson was suddenly inspired, also passing Bourdais for second, with Pagenaud attempting to find a way around his friend and countryman.
As the competition intensified, so did the rain and, when Rahal made his next stop, it was to take on wets. Sadly for the 18-year old NHLR rookie, his haste to rejoin caused him to stall, and the time taken to restart the Medi Zone car was enough to cost him any hope of victory.
Rahal's stop promoted Wilson to the lead, and the Briton appeared comfortable in the changing conditions before being caught out and running wide, dropping to sixth in a trice. Pagenaud, whose move on Bourdais had been successful, then took over, and began to pull away as second-placed Jani came under pressure from both Doornbos and Bourdais, who had pitted shortly before Figge brought out his second safety car of the afternoon on lap 47.
Again, Pagenaud appeared at ease with the conditions as he maintained a decent advantage but, as the rain persisted, the Frenchman was caught out at turn 14, skating perilously close to the gravel and handing the initiative back to Doornbos with just 15 minutes remaining.
Places continued to change, with Wilson succumbing to a determined move from team-mate Tagliani around the outside of turn seven, and Power joining the list of those to pounce on Jani, the Aussie moving up to fourth. Thus when the final yellow flew - again for the hapless Figge - on lap 56, Doornbos headed Bourdais, Pagenaud, Power, Jani, Tagliani, Wilson and Rahal, with Oriol Servia, Ryan Dalziel and Katherine Legge completing the unlapped runners.