On a whim prompted by the frenzy over Wednesday's $340 million Powerball jackpot, the New Hampshire Republican bought a ticket that matched five of the six numbers in the Powerball game.
He collected a $853,492 check Thursday.
Gregg spent $20 on tickets this week at a Washington gas station, allowing the ticket machine to generate his numbers at random. As he was leaving, a clerk ran after him because he had left one of the tickets behind.
"She was a very pleasant young woman. She might have kept it and for all I know it might have been the winning ticket," Gregg said during a news conference conducted by telephone.
The lawmaker said he doesn't buy lottery tickets often but was intrigued by the publicity surrounding the huge jackpot. "Every American believes in good fortune and good luck and I'm no different," he said.
Gregg, 58, said he will donate part of his winnings to the Hugh Gregg Foundation, which supports New Hampshire charities and is named after Gregg's late father, a former governor of New Hampshire.
Meanwhile, all eyes were on Oregon, where someone bought the winning Powerball ticket worth $340 million.
It was the largest jackpot in the game's history and the second-biggest lottery jackpot in U.S. history.
The winning numbers drawn Wednesday evening were 7, 21, 43, 44, 49 and 29.
"We do not know exactly where the ticket was sold," Oregon Lottery spokesman Chuck Baumann told CBS Radio News. "We know that it's a $340 million jackpot ticket, though. That much we do know."
Forty-seven tickets sold matched the first five numbers drawn but failed to match the Powerball. They win $200,000 each, plus a bonus of $653,492. The odds of hitting all six numbers were 1 in 146 million.
If the winner decides to take a lump sum payment, he or she will get "only" more than $110 million after taxes, said Baumann.
"It's 25 percent federal and 8 percent state, so I guess you could say that President Bush and, in our case, Gov. Kulongoski are also winning," Baumann said.
The drawing capped a day of heavy sales in all 27 states where Powerball is played, including North Dakota, plus the District of Columbia and the U.S. Virgin Islands.
The jackpot had been snowballing since mid-August, with 20 straight drawings in which no one won the grand prize.
"We're swimming in it today," said Marianne Ward at the Cash & Dash in Little River, S.C. "We've sold more than $2,000 in tickets since 6 a.m."
Mary Neubauer, spokeswoman for the Iowa Lottery, said hundreds of ticket buyers had played a set of numbers from the ABC drama "Lost," which featured a character who won $156 million by playing a string of digits obtained from a patient in a mental institution: 4, 8, 15, 16, 23 and 42.
"I just think it speaks to people's fascination with numbers and the what-if factor," Neubauer said.
Susie Siebke crossed the Mississippi River from Illinois to buy 25 Powerball tickets for herself and five co-workers. "We only buy just whenever it gets this high," Siebke, 30, said as she stood in line at a convenience store in Bettendorf.
The biggest lottery jackpot in U.S. history was $363 million, won by two ticket holders in Illinois and Michigan in 2000.
And if you have that winning $340 million ticket?
"I would recommend that you just flip the ticket over, sign the back, and then find someone that you trust who knows what to do with large sums of money," Baumann said.