California Chrome won the Preakness Stakes in front of a record 123,000 crowd at Pimlico Racecourse to keep his US Triple Crown chances alive.
The colt, ridden by Victor Espinoza for 77-year-old trainer Art Sherman, ran on strongly to win the race in Baltimore.
Having won the Kentucky Derby on 4 May, California Chrome can become the first Triple Crown winner for 36 years by landing the Belmont Stakes on 7 June.
The feat was last achieved by Affirmed in 1978.
Sent off the 1-2 favourite, California Chrome saw off the challenge of Ride On Curlin, with Social Inclusion in third.
The diminutive winning trainer Sherman has shot to prominence from relative obscurity.
"I'm kind of getting used to it. After I won the Kentucky Derby, I said, 'Wow, all of a sudden I feel like Willie Nelson,' the old rock star coming through the airport," he said.
"Sometimes I need to take my little siesta for about an hour. I just call it charging my battery a little bit."
Jockey Espinoza, 41, won the first two legs of the Triple Crown in 2002 aboard War Emblem but managed only an eighth-place finish in the Belmont Stakes.
"If it was easy a lot of horses would have won the Triple Crown, you know? 30-something years (since the last one), it's just crazy," said the Mexican rider.
"It has to be a super horse to win that. They lose so much energy (having three races in five weeks). Hopefully California Chrome comes back good, and he is the one who can do it."
The rags-to-riches story of California Chrome, a chestnut colt with four white feet, has shades of Seabiscuit - the beloved 1930s horse whose life was made into a Hollywood film.
Owners Steve Coburn and Perry Martin created DAP Racing (Dumbass Partners), bought a mare named Love the Chase for $8,000 (£4,800) and paid a $2,500 stud fee to breed her with Lucky Pulpit, who won only three of his 22 starts.
The result of that modest mating was California Chrome, who won $900,000 for Saturday's triumph to push his career earnings to nearly $3.5 million (£2.1m).