Ed Carpenter scored his maiden IndyCar victory at Kentucky, while Dario Franchitti profited from a pitlane collision for Will Power to reclaim the championship lead by finishing second.
With just one race remaining, the Las Vegas finale, Franchitti now leads Power by 18 points - a dramatic swing as he trailed by 11 heading into Kentucky.
That margin could have been even greater however, with Franchitti being pipped by just 0.0098s as he and Carpenter took the chequered flag in a thrilling photo finish.
Despite losing victory by such a tiny margin the race played perfectly for Franchitti, as slick pit-work from his Ganassi crew allowed him to capitalise on several yellow flag periods and move up from his 11th place qualifying berth.
The key moment came at quarter distance, when Power - who had led every lap thus far - dived into the pits for the first time.
As he aimed for his bay, Ana Beatriz (Dreyer & Reinbold) was released into his path and the pair made contact, damaging Power's left side pod. A yellow flag period for track debris eased the impact as he was able to frequently pit for repairs, but the Penske team could only patch up a gaping hole.
Power rejoined on the lead lap, but was down in 23rd and unable to make progress as the damage affected his car's performance. He eventually came home 19th.
Franchitti had opted to pit several laps later and a slick stop gave him a lead he would then protect until the very closing stages - his cause being aided by a late crash for Beatriz which brought out a lengthy yellow flag period and eased concerns over his need to conserve fuel.
Ganassi's Graham Rahal was not so lucky and had to pit from second 30 laps from the finish, allowing Carpenter to move up into the position from which he challenged, and eventually beat, Franchitti. The 30-year-old had earlier had to drive one-handed when his visor came loose, but held it together to take his first ever IndyCar win.
Power's clash with Beatriz was just one of a number of pitlane accidents. Simona de Silvestro (HVM) started a chain of events as, on cold tyres, she lost control of the rear of her car and speared into the wall at the KV Racing team bay, hitting a team member and causing a long yellow period.
As the field dived into the pitlane Marco Andretti (Andretti Autosports) came in from second, but put himself and Alex Lloyd out as he dived down the inside of the Dale Coyne man just as Lloyd pulled into his pit bay.
Almost simultaneously JR Hildebrand (Panther Racing) ran deep and hit a member of his pit crew, dropping out of a strong fourth position.
Such mistakes helped Ganassi's Scott Dixon finish third ahead of James Hinchcliffe (Newman/Haas), Ryan Hunter-Reay (Andretti), Oriol Servia (Newman/Haas), Wade Cunningham (Sam Schmidt) and Ryan Briscoe (Penske) - all of whom finished within 1s of Carpenter.
Townsend Bell, replacing the injured Justin Wilson at Dreyer and Reinbold, made 15 places on his way to finishing 11th ahead of Rahal, whose race was spoiled by his late stop for fuel.
Dan Wheldon meanwhile finished 14th for Sam Schmidt, an interesting parallel of his Las Vegas mission after he was forced to start from the back of the field for not passing technical inspection.
Results - 200 laps: Pos Driver Team Time/Gap 1. Ed Carpenter Sarah Fisher 1h42m02.7825s 2. Dario Franchitti Ganassi + 0.0098s 3. Scott Dixon Ganassi + 0.1048s 4. James Hinchcliffe Newman/Haas + 0.3007s 5. Ryan Hunter-Reay Andretti + 0.4040s 6. Oriol Servia Newman/Haas + 0.6806s 7. Wade Cunningham Sam Schmidt + 0.7020s 8. Ryan Briscoe Penske + 0.7895s 9. Buddy Rice Panther + 1.0011s 10. Danica Patrick Andretti + 1.0076s 11. Townsend Bell Dreyer & Reinbold + 1.1767s 12. Graham Rahal Ganassi + 1.2320s 13. Charlie Kimball Ganassi + 1.7795s 14. Dan Wheldon Sam Schmidt + 2.0668s 15. Takuma Sato KV + 2.1166s 16. Vitor Meira Foyt + 2.4294s 17. Tony Kanaan KV + 3.0101s 18. Mike Conway Andretti + 3.4607s 19. Will Power Penske + 6.4970s 20. JR Hildebrand Panther + 1 lap 21. James Jakes Dale Coyne + 2 laps 22. Pippa Mann Rahal Letterman Lanigan + 3 laps 23. EJ Viso KV + 8 laps Retirements: Ana Beatriz Dreyer & Reinbold 165 laps Simona de Silvestro HVM 141 laps Alex Lloyd Dale Coyne 140 laps Marco Andretti Andretti 140 laps Dillon Battistini Conquest 124 laps Helio Castroneves Penske 34 laps