Scott Dixon might have entertained a thought that he'd gain some traction in the IndyCar Series championship race with the commanding victory in Sunday's Honda Indy 200 at Mid-Ohio, but that doesn't follow the season's script.

Team Penske's Ryan Briscoe was right behind - figuratively, if not by a close margin - and Dixon's Target Chip Ganassi Racing team-mate, Dario Franchitti, finished third in the 85-lap race so, for the twelfth time in the 13 races, the IndyCar Series points lead has changed hands - not allowing any of the three to build momentum or a sizeable gap heading into the season's final four events. Eight lead exchanges had been the most through the 16-race season in 2003.

Dixon, who's won four times in 2009, heads to the 23 August Indy Grand Prix of Sonoma at Infineon Raceway with a three-point advantage over Briscoe, whose two victories have been augmented by half a dozen runner-up finishes.Franchitti, the 2007 series champion, is 20 points arrears.

It's the third time since 2001 that the top three are separated by 20 or fewer points with four races left - twelve points in 2002 and '03 being the closest - and the closest 1-2 during that same time span. With four races remaining last year, Dixon led Helio Castroneves by 65 points only to see the title decided in the season finale for the third consecutive year. So he isn't taking anything for granted.

"It's the IndyCar Series so, obviously, it will come down to the wire and it's going to be tough," said Dixon, who's lost and won the championship in the final event the past two years, "It's been a strange season in the fact that it doesn't seem like anybody really wants to lead the championship. There's been some flopping back and forth between myself and Dario and Ryan and TK [Tony Kanaan], so it's been quite interesting.

"I think it's quite obvious that it's going to come down to Homestead. We've got a great mix of circuits yet to come, with a road course and a few ovals, so it's going to be a tough championship."

Following Infineon, there are 1.5-mile oval events at Chicagoland Speedway, Twin Ring Motegi in Japan and Homestead-Miami Speedway, and Briscoe will be among those heading to California to test alongside his title rival. The Australian will be sharing a car with Penske team-mate Helio Castroneves during the 12-13 August session.

"I'm really excited to be in the championship," Briscoe admitted, "It's been a fantastic year. It's definitely intense and can get frustrating at times. You look back on races, and, for me, it's ones like Richmond where I only got twelve points. If I could have gotten a top five or something, what the difference could be.

"But that's where you just need to keep looking ahead and keep your head down. You've got to finish these races and finish at the front and just stay focused. I like the next four tracks we're going to. It's going to be exciting and it's probably going to be [close] to the end."

Each of the three contenders has started from the pole at Infineon i the past - Briscoe in 2005, Dixon in '06 and Franchitti in '07 - while Dixon won there in 2007 from the fifth starting spot. Franchitti has finished second and third in his past two races on the natural-terrain course, while Briscoe started and finished second last year.

"I don't really care for leading the championship at this point," Dixon said matter-of-factly. "The only time you want to lead it is at the end."