For the second consecutive year, excitement is building about a potential Triple Crown in horse racing.  Yet for American Pharoah to win Saturday evening’s Belmont Stakes and become the 12th horse in history to sweep the three major races needed to pull off the feat, he’ll have to overcome nearly 40 years of also-ran status. No horse has managed to win the Crown—whose races also include the Kentucky Derby and the Preakness Stakes—since Affirmed did it in 1978.  To win a Triple Crown, a horse has to run the three races in a short span, without the customary rest. He must beat rivals who typically don’t run in all three races and are fresher. And he has to endure the longest of the three races in the final leg, the Belmont, where even stout contenders sometimes run out of gas down the stretch.  Despite these inherently long odds, American Pharoah will likely go off at post time as the betting favorite as hopeful fans stake a claim to potential history. “The Triple Crown brings out the instinct to root for something that hasn’t been done” in decades, said Penny Chenery, who owned 1973 Triple Crown winner Secretariat.  Short odds at the betting window, however, don’t translate into short odds out on the track.  For American Pharoah, the Belmont will be his third race in five weeks. That is not much downtime for today’s elite thoroughbreds, which typically race just once a month to allow time for recovery.  And American Pharoah will be the only horse competing in all three Triple Crown races. After the Derby, there is only one horse left with a chance to win the Triple Crown. So many horsemen opt to skip the Preakness, contested two weeks later, and wait for the Belmont, which comes five weeks after the Derby.  “If they don’t feel like they can handle him two weeks later, why not wait, freshen up a little bit,” said American Pharoah’s trainer, Bob Baffert. “Basically, catch him when he’s already pitched eight innings.”  Then there is the endurance challenge of the Belmont itself, which isn’t just the final race in the Triple Crown series, but also the longest. Nicknamed the “Test of the Champion,” it is a 1½-mile race, compared with the 1¼ miles for the Derby and 1 3/16 miles for the Preakness.  “The better the horse, the harder it is to tell if the previous races have taken a toll,” said Hall of Fame jockey and current NBC Sports analyst Jerry Bailey. “A lot of times, even as a jockey, you don’t know until you ask your horse for their best turning for home.”  Still, the tendency of some owners to rest their horses for a shot at picking off a would-be Triple Crown winner like American Pharoah is irksome to some.  Last year, California Chrome won the Derby and Preakness but lacked a closing kick in the stretch of the Belmont, finishing in a dead-heat for fourth about two lengths behind the winner Tonalist.  California Chrome co-owner Steve Coburn suggested that his horse had been worn down by the rigors of running three hard races, while Tonalist was a newcomer to the Triple Crown series.  “It says Triple Crown. You nominate your horse for the Triple Crown. That means three,” Mr. Coburn said after the race.  While Mr. Coburn may have been correct that a fresher horse held the advantage over his horse, he was mistaken in the assumption that more horses used to run in all three Triple Crown races.  The last Triple Crown winner, Affirmed, faced only one horse, Alydar, in all three races in 1978. Two horses, Run Dusty Run and Sir Sir, challenged Seattle Slew in 1977 in all three races, while only Sham lost to Secretariat three times in the 1973 Triple Crown.  “That part of the Triple Crown doesn’t bother me at all,” said Mr. Baffert, who plays down any disadvantages for American Pharoah. “That is what this test is all about.”  But there are obstacles today that were lesser during the run of Triple Crown victors in the 1970s. As the purse size for the premier races has increased, so has field size. Secretariat beat 12 rivals in the 1973 Kentucky Derby to earn a little more than $150,000, which is about $800,000 in today’s dollars. American Pharoah’s win over 17 horses earned $1.4 million.  A larger field makes it statistically more difficult to win, as increased traffic leaves the possibility of getting caught behind a tiring horse or shut off along the rail with less room to run.  The average field size that the 11 Triple Crown winners faced in the Belmont was 5.4. Eight horses are expected to enter the starting gate on Saturday. Citation in 1948 and Seattle Slew in 1977 are the only two horses to win the Triple Crown beating at least seven challengers in the Belmont.  Also, a wider range of horses have run in at least one Crown race in recent years. Last year, 30 different horses ran in at least one. In 2008, when Big Brown attempted to sweep the series, 33 different horses ran. By comparison, only 17 different horses ran in at least one Triple Crown race in 1973, the year Secretariat romped by 31 lengths in the Belmont.  One stat that could be to American Pharoah’s advantage and be attributed to his dominant form in recent races: Only 22 different horses will have competed in at least one Triple Crown race this year, the fewest since 1997.  Still, while Mr. Baffert said American Pharoah was “doing well” in the days leading up to the big race, he allowed that he wouldn’t mind if fortune smiled his way. “We still need a bit of racing luck.”  Write to Jim Chairusmi at jim.chairusmi@wsj.com
The Numbers: American Pharoah has a shot at racing glory in Saturday’s Belmont Stakes, but securing the Triple Crown will require him to overcome some long odds.