Ganassi's Dario Franchitti is fending off Penske duo Helio Castroneves and Ryan Briscoe for the race lead at the half-distance point in the 2010 Indianapolis 500.
The Scot moved up from third to first before the opening lap was complete, and has been the main protagonist ever since, leading 93 of the first 100 laps.
Behind the top three, Ed Carpenter has been a frontrunner all afternoon for Panther/Vision Racing and is fourth, while Andretti Autosport's Tony Kanaan has mounted an incredible charge from the back row to run fifth, followed by the impressive Tomas Scheckter (Dreyer & Reinbold).
The first half of the race saw several big names hit trouble in the pits. Will Power had battled for the lead with Franchitti initially but pulled away from his first pitstop too soon - ripping part of the fuel hose away with him, which meant both an additional stop and a penalty. He has climbed back into the top ten since then.
Scott Dixon then fell from the top six to the tail of the lead lap pack when he shed his left front wheel in the pits as he left following his second stop.
Davey Hamilton became the race's first retirement when he spun out of Turn 2 on the opening lap. Bump Day star Bruno Junqueira did not last much longer, crashing the Fazzt Dallara on lap seven.
Also in the wall early were John Andretti (Andretti Autosport), Mario Moraes (KV), and Raphael Matos, who had starred for De Ferran Dragon at first, running as high as third before losing a wheel in the pits. He rejoined but crashed heavily soon after.