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Graham Rahal doesn't have to think hard to answer why the IZOD IndyCar Series has been so competitive in 2012. All he has to do is look back to the series' last race - the Honda Indy 200 at Mid-Ohio and he has the answer.

"I don't know if I've seen a field that is that competitive or that close worldwide," the second-generation driver said. "At Mid-Ohio, you're talking about a track that's over a couple miles long, with lots of elevation (changes), and with different engines, different teams. The whole thing. If you missed by a tenth and half in qualifying, like we did, you start 22^nd. That's how competitive it is. We weren't far off the pole time and we were that far back. It shows how the quality of the driving has gone up. You have to be on top of your game every session of every race."

With three races to go entering this weekend's GoPro Indy Grand Prix of Sonoma, there are 15 drivers, including Rahal, still mathematically eligible for the IZOD IndyCar Series championship.

It's the most since 2000 when 24 drivers were still mathematically eligible to win the title with three races remaining in a nine-race season. And while there are 15 races on the 2012 slate, another of the title-contending drivers, Panther/Dreyer & Reinbold Racing's Oriol Servia, said 2012 has been the most competitive Indy car racing season he's experienced.

"I've had seasons with very competitive fields, but it really seems this year that all the best drivers of CART, Champ Car and IndyCar have gotten together. There's not one driver of the top 20 that could not win the race," Servia said. "You see it in qualifying. You could be fighting to be in the top six or you could be 18th. And those in the middle are very close. In qualifying, you feel as if you really have to give everything you have to make the top six. You feel empty after because it's such a challenge physically and emotionally. When the competition is that high, it just takes you to a level you didn't know you could reach. It's part of the addictive thing that we do."

Team Penske's Will Power, who leads the series point standings by five over Ryan Hunter-Reay, said the introduction of the 2012 IZOD IndyCar Series chassis and the ability to run closer together has raised the level of competition on both ovals and road/street courses.

"It's insanely competitive," the two-time series runner-up said. "You haven't seen anyone consistently win poles or win races. No one dominates this series. It just proves how tough it is and tight it is. You have to work on all the finer points of your driving just to be competitive. Anyone in any other series in the world could come here and I can guarantee you it would take them a good year to get competitive, if they are a good driver."

Any driver within 107 points of the lead will remain eligible for the championship as the series heads to Baltimore on Sept. 2. But the closeness of the competition among drives almost assures that the title race will go down to the final race of the season for the seventh consecutive season.

"It's the beauty of the series going from a road course to a street course to a fast oval," Servia said. "It's what I've always loved about (Indy car racing) - the mixed schedule. Teams have to change a lot of different things in the car and the drivers have to have different skills. I love the challenge and love that we show the challenge to the fans. The championship will be a fight to the end."

Did You Know: 2012 IZOD IndyCar Series Championship

Drivers still eligible for championship: 15

Key Championship point statistic: The 15 championship-eligible drivers with three races to go is the most since 2006 when there were 13 drivers eligible. The most was in 2000 when 24 drivers remained eligible, but the schedule was made up of nine races compared to this season's 15- race schedule.

Closest 1-2 point differential since: 2011. With only three races to go, the 2012 points battle (5 points separate first and second) is the same as it was in 2011 when Dario Franchitti led Will Power by five points. The average point deficit with three to go since 2006 is 18.7 points.

Championship-eligible drivers with strong results at Sonoma: Dario Franchitti has six starts at Sonoma with an average finish of 3.5. Scott Dixon has made seven starts at the facility with an average finish of 6.3. Helio Castroneves and Franchitti each have five top-five finishes. Will Power has two wins in the three starts he's made at Sonoma.

Championship-eligible drivers with poor results at Sonoma: Ryan Hunter-Reay has historically struggled at Sonoma. Hunter-Reay has never finished in the top-five at Sonoma in five previous starts. Simon Pagenaud finished 15^th in his only start at Sonoma and JR Hildebrand's average finish in Sonoma is 23.5.

Charting the leaders: With 53 maximum points available at Sonoma, the points lead could change as it did at Mid-Ohio on Aug. 5. The championship lead has exchanged hands four times this season (see chart below). The leaders: Helio Castroneves (St. Petersburg-Barber); Will Power (Long Beach-Toronto); Ryan Hunter-Reay (Edmonton); Will Power (Mid-Ohio).

One-race positioning: Will Power went from third in points after Edmonton (26 points behind) to first at Mid-Ohio with a runner-up finish in the Honda Indy 200 at Mid-Ohio. Scott Dixon went from 61 points behind at Edmonton to 28 points behind with his win at Mid-Ohio.

Championship chases with three races left:

2011

Leader: Dario Franchitti (507). Second: Will Power (-5). Scott Dixon (-77)

Final Margin and Champion: 18 points. Dario Franchitti

2010

Leader: Will Power (528). Second: Dario Franchitti (-23). Third: Scott Dixon (-85)

Final Margin and Champion: 5 points. Dario Franchitti

2009

Leader: Ryan Briscoe (497). Second: Dario Franchitti (-4). Third: Scott Dixon (20)
Final margin and champion: 11 points. Dario Franchitti

2008

Leader: Scott Dixon (558). Second: Helio Castroneves (-78). Third: Dan Wheldon (-138)
Final margin and champion: 17 points. Scott Dixon

2007

Leader: Dario Franchitti (518). Second: Scott Dixon (-8). Third: Tony Kanaan (-52)
Final margin and champion: 13 points. Dario Franchitti

2006

Leader: Helio Castroneves (376). Second: Sam Hornish Jr. (-8). Third: Dan Wheldon (-17)
Final margin and champion: Tie between the three. Hornish won by virtue of most victories