By Michele D. Manigault
Ruppersberger defeated four others to claim the Democratic nomination.
Ruppersberger defeated Oz Bengur, a Timonium investment banker, 32,307 votes to 23,436, with 100% of precincts reporting.
Three other Democratic challengers - Brian Davis, James DeLoach Jr. and Kenneth Bosley - were not factors in the election results.
Ruppersberger told supporters at the Timonium Holiday Inn that his race was about "believing in what's right for families and the people of Maryland."
The two-term county executive now advances to meet the Republican nominee - former U.S. Rep. Helen Bentley - in a much-anticipated general election showdown.
Bentley, who served five terms in the U.S. House, until she ran for governor in 1994, defeated challenger Scot Young in the GOP primary, 19,043 to 4,781, with 100% of precincts reporting.
In the 1st Congressional District, the negative campaigning between incumbent Republican Rep. Wayne Gilchrest and challenger Dave Fischer ended with a decisive win for Gilchrest.
Gilchrest captured 34,509 votes compared to Fischer's 20,946, with 100% of precincts reporting.
"I appreciate the voters putting trust in me one more time," Gilchrest said. "I am looking forward to serving the county for two more years and am ready to work again."
In the general election, Gilchrest will face Democrat Ann Tamlyn, who ran unopposed in the primary.
There were few surprises in the 7th District Congressional race, where incumbent Rep. Elijah Cummings trounced three challengers to win the Democratic nomination.
"We realize that we have a lot of work still to be done," said Cummings early in the evening at a campaign party in Canton.
In November's general election, Cummings will face Republican challenger Joseph Ward of Hunting Ridge, who ran unopposed in the GOP primary. Four years ago Ward - then a Democrat - lost the 7th District primary to Cummings.
"I'm very optimistic about the General Election," said Ward. "I really believe I'm going to win."
Meanwhile, Rep. Ben Cardin, the 3rd Congressional District incumbent Democrat, also basked in the glow of a landslide victory to earn the party's nomination against challenger John Rea, 61,423 votes to 6,824 with 100% of precincts reporting.
"This was a great day for the Democratic party," said Cardin.
But as Cardin was celebrating his victory, his probable GOP challenger was making plans for his own celebration.
Scott Conwell, an Anne Arundel County resident and attorney who practices in Washington, D.C., topped fellow Republican Michael Jackson, 16,851 votes to 4,520, with 100% of precincts reporting.
In the 6th District, with 100% of precincts reporting, Donald DeArmon won the Democratic nomination by a slight margin of 16,548 votes to 15,134.
Even though the numbers were in doubt early on, DeArmon, who faced Bartlett in 2000, was confident that he'd get another try.
"I'm pleased to have a rematch with Roscoe," said DeArmon, a congressional staff assistant for California Rep. Lucille Roybal-Allard.
Roscoe Bartlett, who was elected in 1992 to represent Maryland's 6th District, ran unopposed in the Republican primary.
Bryan Sears, Jennifer Przydzial and Pat van den Beemt contributed to this story.