Former Republican and Reagan military aide James Webb won the Democratic nomination for a U.S. Senate seat in Tuesday's Virginia primary.

Webb, a decorated Marine rifle company commander in Vietnam, will challenge Republican Sen. George Allen, whom he endorsed just six years ago.

With more than 80 percent of the vote reported, Webb held 54 percent of the vote over longtime Democratic activist Harris Miller. Webb pulled ahead in a seesaw race with a huge boost in the suburbs of Washington, D.C., the state's most populous region where the turnout was heaviest.

Webb, who broke with the Republicans over the invasion of Iraq and what he says are economic policies that bleed the middle class, said support from senior U.S. Senate Democrats was important to his victory.

"Everywhere I went, I had to face a room where people wondered if I really was a Democrat. When these people stepped forward to endorse, they were saying they were comfortable with my values," Webb said in a telephone interview with The Associated Press.

Miller, a wealthy businessman and former Washington lobbyist, put nearly $1 million of his own money into the campaign and outspent Webb by more than a 2-to-1 ratio.

"He had a lot of money and a lot of mailings," Webb said. "Where we were able to go sit with people, we were able to do really well."