Three races in a five-week span at varying distances on different tracks. It's so tough only 11 horses have won the Triple Crown, and none in 36 years.

It's the longest span without a winner. Now it's California Chrome's turn to try.

The striking chestnut colt appears to have rebounded well after two hard races in the Kentucky Derby and Preakness, with the most exhausting still to come. He'll run 1-1/2 miles (2400m) around Belmont's sweeping oval on Saturday (Sunday AEST) with 10 rivals gunning to keep history from happening.

Before Affirmed won the Triple Crown in 1978, 25 years had passed between Citation in 1948 and Secretariat in 1973.

Few can agree on what makes winning the Triple Crown so tough. Often it's a combination of factors that help or hurt a horse, including racing luck and jockey error.

In 2002, War Emblem nearly fell to his knees when the starting gate opened, and jockey Victor Espinoza knew then the colt was doomed. He straggled home in eighth place, beaten 19-1-2 lengths.

Espinoza gets another shot on Saturday aboard California Chrome, who, if he wins, will have faced down the largest field of any Triple Crown winner.

Bob Baffert, the only trainer to lose the Belmont three times with horses that won the first two legs, including War Emblem, said the Art Sherman-trained California Chrome needed to make a good start.

"It doesn't matter if there are 14 or six horses. He needs to break clean," Baffert said.

"With a clean break, he's way better than all the other horses."

California Chrome had been slow out of the starting gate in some of his earlier races because of his habit of shifting from one foot to the other. Espinoza will try to keep his head pointed straight and get him to show some early speed leaving the gate.

Sherman often describes California Chrome as a "push-button horse". Tactically, he can run on or near the lead or make a move for the front in the latter stages of a race, like he did in the Derby and Preakness.

"He's going to probably be galloping on the lead," Sherman said. "He doesn't want any horse passing him."

California Chrome has given every indication in his gallops and one official work-out at Belmont Park during his nearly three weeks in New York that he likes the deep, sandy track.

"I just like what I see. He looks so darn good," Sherman said. "People have a lot more respect for this horse than they did going into the Derby. I really think he's the real McCoy."

The distance could catch up with California Chrome whose modest pedigree suggests he can't do what he's already done. Now it's a question of whether he can run an extra quarter of a mile in the Belmont.

Of course, 10 other horses will have a say in what happens.

"California Chrome is a horse that's going for history, and we're all trying to throw something in his way," Samraat's trainer Rick Violette said.