ELMONT — Two-thirds of the work is already done. Early this evening, at what is expected to be a crowded and electric Belmont Park, Kentucky Derby and Preakness winner Big Brown will go after one of the most elusive prizes in sports.

A victory in the 140th Belmont Stakes, one his trainer has already called a “foregone conclusion,” would make Big Brown the 12th Triple Crown winner in history, and the first in 30 years.

Should any of his nine rivals spring what would amount to a colossal upset, Big Brown would become the 19th horse to have his shot at immortality dashed in the series’ last and longest leg.

“I’m doing good. He’s doing good,” trainer Rick Dutrow Jr. said Friday morning outside barn 2, where Big Brown has taken up residence for the past three weeks. “Anytime you have a horse running for a Triple Crown, it’s got to be exciting.

“It looks like Big Brown has a really good chance of doing it, so there’s excitement in the air. He’s a special horse. He’s just the coolest horse that I think ever lived.”

Owned by IEAH Stable and Paul Pompa Jr., Big Brown is the 2-5 program favorite in the 11⁄2-mile Belmont, carded as the 11th of 13 races today, with an estimated post time of 6:25 p.m.

Undefeated in five career starts, Big Brown is out to join Seattle Slew as the only horses to win the Triple Crown without a loss.

Under Hall of Fame rider Kent Desormeaux, Big Brown will break from post position No. 1, which has produced nearly twice as many Belmont winners (23) than any other. The last horse to win from there was Empire Maker, who ended Funny Cide’s Triple Crown bid in 2003.

Stabled with Hall of Fame trainer Bobby Frankel rather than the rest of Dutrow’s string at Aqueduct, Big Brown was given Empire Maker’s old stall.

“Frankel told me that this horse is blessed, and I believe him,” Dutrow said. “The hits keep on coming for us. They just keep coming. It’s all good.”

None of the previous Triple Crown champions won their clinching race against as many horses as Big Brown will face today. The existing benchmark is shared by Citation in 1948 and Seattle Slew in 1977, who both beat seven rivals.

“I’m just looking for him to win,” Dutrow said. “I don’t care how many are behind him or who’s second. He’s a very brilliant horse. He knows something’s going on. He knows it’s coming, and that’s a very good thing.”

Following Affirmed’s victory in 1978, 10 horses have won the Derby and Preakness but lost the Belmont, six since 1997. Two of them were upset by horses ridden by jockey Edgar Prado, who won with Sarava ($142.50) in 2002 and Birdstone ($74) in 2004.

Prado has the mount today on Kentucky-bred Japanese import Casino Drive, the unbeaten Peter Pan winner who many believe could be the only obstacle for Big Brown. A half-brother to the past two Belmont winners, Casino Drive came down with a possible foot bruise in his left hind hoof Friday morning, however, which could cost him the start.

“You want to go over there with a chance to win the race,” Prado said. “Other than the purse, it’s the prestige of winning a Triple Crown race. There’s nine other horses that want to do that. Second and third, nobody remembers that.”

Among Big Brown’s foes are three from the Derby in Denis of Cork (third), Tale of Ekati (fourth) and Anak Nakal (seventh); Macho Again and Icabad Crane, who ran 2-3 in the Preakness; and Ready’s Echo, Da’Tara and the maiden Guadalcanal, none of whom ran in the first two legs.

“Big Brown is absolutely awesome,” Denis of Cork’s trainer David Carroll said. “We’re looking for any way we can beat him. Obviously, it’s a tough task, but we’re here to win, and we’re going to give it our best shot.”

Last year’s Belmont was won by the filly Rags to Riches, who beat eventual Horse of the Year Curlin in a thrilling stretch duel. She was trained by Todd Pletcher, who will saddle Ready’s Echo.

“Certainly, it appears Big Brown has been head and shoulders above everything that’s run in the Derby and Preakness, and everything else, for that matter,” Pletcher said. “We need him to come back to us a bit, and we need somebody to love the mile and a half and maybe him not love it. We need something to even out to beat him.”

The issue of a healed and patched quarter crack on his left front hoof apparently behind Big Brown, Dutrow feels that the big, bay Boundary colt is sitting on history.

“Everybody’s seen him run,” he said. “He’s beaten mostly every horse in the race with ease. He’s just got a couple newcomers, and I don’t think they add up to much against our horse. I got nothing to worry about, only the horse, and the horse is doing great.

“They’re going to have to show up, because I know our horse is going to show up. Anybody that’s going to try to beat him, they’re going to have to run the race of their life, something you’ve never seen out of them before. We’ll just have to see about that. I’m looking at the field, and I have a lot of con­fidence that our horse can get the job done.”