A single card made a difference of almost $700,000 to Alex Jacob ’06, when he went all in with a king and a jack in the final hand of the World Poker Tour tournament at Foxwoods Casino on Sunday night.

A jack fell on the “river,” the fifth community card in Texas Hold ‘Em, giving Jacob a pair with a king as the kicker. But his last remaining opponent, Victor Ramdin, had called Jacob’s all-in and flipped an ace and a jack.

The hand — and the tournament — came down to the difference between an ace and a king, since both players had a pair of jacks.

Jacob took home $655,507 for his second-place finish in the tournament, which lasted for 120 hands throughout four days. The televised event dispensed more than $4 million in prize money and drew 431 contestants, who each paid $10,000 to play in the tournament.

Three hands before he lost the tournament, Jacob was the chip leader. But he gave up the lead when Ramdin went all in and won on the 118th hand of the event to double his chip stack.

Tom Lehman ’06, who traveled to Foxwoods, about 50 miles north of New Haven, to watch his friend compete in the final day of the event, said there were only two big hands after the field was reduced to two players, but Jacob lost both of them.

“The fact that it came down to one hand … was just incredible,” he said.

Ramdin — who won $1,331,889 last night and earned a seat at the World Poker Tour Championship — had competed in three earlier WPT events, earning a total of $100,538 in seasons two and three of the series.

Ariel Schneller ’06, who has played poker for several years in casinos and on the Internet, said Jacob is one of the five best poker players he has ever played with.

“This isn’t just some college kid who you read about who got lucky at a tournament,” Schneller said. “He’s legitimately a poker professional.”

Matt Kennard ’06 hosts a popular regular poker game in Saybrook College, but he said there are few players on campus who play for the same high stakes as Jacob. At Jacob’s level, Kennard said, players rarely make major avoidable mistakes, although they might lose because of an error in timing.

“At that level, those players can be very consistent with their play and their reads are going to be solid,” Kennard said.

Poker’s popularity — especially that of Texas Hold ‘Em — has grown enormously in recent years, fueled by the availability of online poker games and ESPN’s televised coverage of the World Series of Poker. Last year, Andrew Baker ’07 won $80,000 for placing first in an online tournament run by PokerStars.com.