Rep. Ben Cardin, a long-serving House member who voted against the war in Iraq, won the Democratic nomination to replace Maryland's retiring Democratic Sen. Paul Sarbanes.
Cardin edged out his closest competitor, former NAACP head Kweisi Mfume and 17 other candidates with 93 percent of the precincts reporting.
Cardin will face Republican Lt. Gov. Michael Steele in November.
Cardin stopped short of declaring total victory in remarks to supporters early Wednesday at a downtown Baltimore hotel, but he said, "I believe I have won this election."
Exercising similar caution, Mfume didn't concede the race when he spoke to his volunteers, friends and relatives shortly before Cardin's appearance. "It's how you finish -- and we're not finished!" he said. But he acknowledged that victory was unlikely and said Cardin would "be a damn good senator representing the state of Maryland, absolutely."
Extended hours
Judges extended voting hours in Baltimore and nearby Montgomery County by one hour because of problems that delayed the opening of some polling places. Officials said some election judges did not show up on time and others had trouble getting into the facilities.
Ruling on a request from county Board of Elections, Circuit Judge Eric Johnson said the polls should remain open for an extra hour, according to county spokeswoman Donna Bigler and Johnson's office.
Polls in the rest of Maryland closed at the normal time of 8 p.m.
Election officials in the state’s biggest jurisdiction failed to deliver computer cards to the county's precincts that would start the electronic voting machines. That meant voters had to use provisional ballots while the county scrambled to deliver the electronic cards after polls had opened at 7 a.m. Fearing that voters would not have enough time to vote because of the glitch, a host of candidates called Tuesday for extending the voting hours.