He raced full-time in the Cup Series the following year, struggling at first, with eight top-ten finishes over his first three seasons and a top points placing of 28th (in 2009).

Hornish began racing go-karts at age 11,[2] winning the World Karting Association U.S. Grand National championship in less than four years.

At the season-opening Grand Prix of Miami at Homestead-Miami, he qualified in the pole position and led for 166 of 200 laps to win his fourth career race in the series.

[32] After the change Hornish's results began improving; he started fourth and finished second, after leading for 126 of 200 laps, at Michigan International Speedway.

[35] Going into the season-ending Chevy 500 at Texas Motor Speedway, Hornish was mathematically eligible win the championship; however, his car had a spray problem after 176 of 195 laps.

6 Dallara IR03-Toyota Indy V8, winning the season opener at Homestead-Miami in his first race with the team, passing teammate Hélio Castroneves on the final lap.

His season highlight was the Indianapolis 500, when he passed Marco Andretti for the lead on the final lap to win[2] in the second-closest margin of victory in the race's history.

[51] In the season-ending race at Chicagoland Hornish qualified for the pole position and finished third, clinching his third series championship[52] and Penske's first.

[54] Hornish's only win of the season was the Bombardier Learjet 550 at Texas Motor Speedway, when he started in second place and led for 159 of its 228 laps.

[55] His series-best finish on a road course or street circuit, second place at the Camping World Watkins Glen Grand Prix, was overshadowed by an altercation with Tony Kanaan.

[60] In November 2013, Hornish declined an offer to drive for Chip Ganassi Racing in the upcoming season after Dario Franchitti's career-ending injuries at the 2013 Shell-Pennzoil Grand Prix of Houston.

Starting in the pole position,[75] he led the first 29 laps of the race before being passed by eventual winner Erik Darnell[76][77] and finishing second.

A lot of people have asked me what the toughest transition is, coming over here from the IndyCars and doing these stock car races, and really it's the fact I don't get much practice time.

[83] Before the season, Penske swapped cars and owners' points with Kurt Busch; Hornish was guaranteed a starting position in the first five races and Busch, who won the series championship in 2004, would also be guaranteed a starting position as the most recent series champion driving a car outside the top 35 in owners' points.

[93] Late in the season his Penske team dropped out of the top 35 in owners' points, and Hornish failed to qualify for the AMP Energy 500 at Talladega Superspeedway and the season-ending Ford 400 at Homestead-Miami Speedway.

[97] Hornish's best finish of the season was eleventh place in the Diamond Hill Plywood 200 at Darlington Raceway, where he started twelfth.

[98] In the Carquest Auto Parts 300 at Lowe's Motor Speedway he led his first laps of the series (eight), but a mid-race accident relegated him to 39th place.

[111] After the season Hornish's longtime sponsor, Mobil 1, left him and Penske for Tony Stewart and Stewart-Haas Racing.

[112] In the 2010 Nationwide Series he drove the season-ending race at Homestead-Miami[113] for Brian Keselowski Motorsports (in conjunction with Penske) in its No.

Allmendinger qualified in eighth place, but due to the driver change Hornish had to move to the rear of the field.

[138] During the season, car owner Roger Penske said that Hornish (who had driven for the team since 2004) would be released due to a lack of sponsorship.

[154] In the GEICO 500 at Talladega Superspeedway, Hornish had a season-best sixth-place finish;[155][156] after the race, Kevin Manion replaced Drew Blickensderfer as his crew chief.

[156] He later finished in the top ten at both road-course races (tenth and ninth at Sonoma Raceway and Watkins Glen International, respectively).

[163] On May 11, 2016, an article posted online by Sports Illustrated appeared to acknowledge that Hornish had retired from racing after being released by Richard Petty Motorsports, saying he "unharnessed himself one last time" and "hung up his helmet at the end of last season.

"[165] On June 8, 2016, Richard Childress Racing announced plans to add Hornish to their Xfinity Series driver lineup, hiring him to drive the No.

[172] At Mid-Ohio, Hornish won the pole, and proceeded to lead 61 of the 75 laps en route to victory in his home state.

[2] During a race weekend at Texas Motor Speedway, Hornish (an avid bowler) promoted a charity bowling event.

with Regis and Kelly,[185] and he was a guest on the September 12, 2006 Late Show with David Letterman after winning the 2006 IndyCar Series championship.

[188] Two years later he was a color commentator for the NBCSN broadcast of the IndyCar GoPro Grand Prix of Sonoma,[189] and was a NASCAR analyst for Fox Sports 1 throughout the season.

* Season still in progress 1 Ineligible for series points (key) (Bold – Pole position awarded by qualifying time.