Hagan, a state senator from Greensboro, immediately invited the support of voters who backed her chief rival, Chapel Hill entrepreneur Jim Neal. Neal had galvanized liberal activists in the party in part through his willingness to candidly discuss he was gay.
Neal, who carried 18 percent of the vote, had repeatedly dismissed Hagan as a political insider. Neal argued that he was the only candidate with the ability to defeat Dole, a national political figure who has worked in two presidential cabinets.
Neal's campaign did not immediately return a call Tuesday night seeking comment.
Dole, first elected in 2002, easily cruised to a win in the GOP primary to defeat challenger Pete Di Lauro of Weldon. She received 90 percent of the votes.
"I look forward to an ongoing dialogue with folks from Manteo to Murphy and asking them for the privilege of representing them in a second term," Dole said in a statement provided by her campaign.
Three other Democrats ran in the primary. Lumberton attorney Marcus Williams picked up 13 percent of the primary vote, while Lexington truck driver Duskin Lassiter had 5 percent, and Moncure podiatrist Howard Staley had 4 percent.
Hagan, 54, has been a state senator for almost a decade and has served as one of the body's chief budget writers for three terms. She previously worked at NationsBank after earning a law degree at Wake Forest University, but she left the job after the birth of her third child.
Coming into Tuesday's primary, Hagan led the race in both polls and fundraising, winning the support of party regulars and repeatedly focusing her campaign on Dole instead of Neal. She raised $1.5 million and purchased a series of television advertisements across the state to boost her name recognition.
Neal, meanwhile, raised about $367,377, a third of which came from a personal loan to his own campaign. He couldn't afford to buy television time, but sought the support of party activists.
Neal was the first Democratic candidate, declaring his willingness to challenge Dole after a series of party leaders declined to get into the race. Among those who demurred: Gov. Mike Easley, Attorney General Roy Cooper and Rep. Brad Miller.
Even Hagan initially backed away. But three weeks after she decided against running, and not long after Neal disclosed he is gay, she reconsidered and joined the race.
Hagan said she needs to raise about $10 million to challenge Dole, a former secretary of Labor and secretary of Transportation who went on to lead the American Red Cross. Her husband, Bob, was the Republican presidential nominee in 1996, and she ran for the White House herself in 2000.
Dole has already set aside about $3.2 million for her re-election bid.