The board will now be divided 3-2, with Republicans still in control because the Democrats who won in 2008 are no longer on the board.
Even as they made inroads in Burlington County, Democrats held their own in races for countywide offices in Camden and Gloucester Counties.
During the campaign, Belgard and Schwartz attacked the incumbents' votes in favor of selling a county-run nursing home for the poor to a private operator for $15 million, calling it a "quick fix" to a budget deficit. The Republicans said the Buttonwood Hospital was a drain on county finances.
The Democrats also criticized their opponents as "rubber-stamping" millions of dollars in cost overruns on projects such as the county library expansion. They said a minority voice on the freeholder board would bring more transparency.
Belgard, an Edgewater Park committeewoman and lawyer, ran unsuccessfully for freeholder in 2010, while Schwartz, a retired nursing home administrator from Southampton, was a newcomer to politics.
Garganio, a union carpenter from Florence, and O'Brien, a lawyer and former Medford councilwoman, were each seeking their second three-year term.
"I'm thrilled. Our hard work paid off. I really feel Burlington County was ready for a change," said Belgard.
Schwartz said: "Everywhere we went, we heard how people were upset by the sale of Buttonwood. . . . People were put out of work and selling Buttonwood struck fear into people's hearts."
In the unofficial tally, Belgard was the top vote-getter, with more than 92,000 votes, followed by Schwartz with nearly 89,000. Garganio garnered nearly 84,000 votes and O'Brien nearly 83,000.
In an e-mail, Garganio said while he and his running mate failed to win reelection, "we helped people, the property taxpayers of Burlington County, at a time when they needed it most."
In Camden County, Republicans' attempt to gain three seats on the seven-member all-Democratic freeholder board failed.
Incumbents Ian Leonard and Jeff Nash and newcomer Michelle Gentek, a former Gloucester Township councilwoman, were winners in an unofficial tally. Nash was the top vote-getter, with nearly 117,000, followed by Gentek with over 113,000 and Leonard with nearly 111,000. Their Republican challengers, Ian Gill, Eugene Lawrence, and Jim Pearce, received fewer than 60,000 votes each.
Nash, who was elected to his eighth term, said he still has the same passion that he did when he first ran in 1991. His focus this time around is keeping taxes down and seeing through the creation of a county police force for which only Camden City has signed up so far.
"We have a responsibility to protect the citizens of Camden," Nash said, adding that the way to do that is with a county police model. "The votes reflect the same opinion."
Nash is a lawyer with the Cozen O'Connor firm. Leonard is the state political director of the International Brotherhood of Electrical Workers.
Newcomer Gentek, 44, a public-relations executive for the New Jersey lobbying and consulting firm Fox & Shuffler, said she wanted to make the county more energy sustainable.
Also keeping his Camden County sheriff title, which he has held since 2006, was Democrat Charles Billingham. Republican Christine Leone-Zwillinger, a lawyer who has been a vocal opponent of the county police force, lost her second attempt to win the job.
"This county has a voting habit and they can't break that habit," Leone-Zwillinger said. "People are so involved with their day to day lives and . . . so focused on top of the ticket that they miss a lot of local nuisances."
The Democrats also retained their 5-2 control of the seven-member Gloucester County Freeholder Board with the reelection of incumbents Robert M. Damminger of West Deptford and Giuseppe "Joe" Chila of Woolwich.
Damminger, a South Jersey Transportation Authority director who has been a freeholder for 15 years, and Chila, a union electrician who has served six years, defeated Republican challengers Margie Love of Washington Township and Tom Thistle of Harrison Township.
Damminger received more than 72,000 votes, followed by Chila with nearly 71,000. Love got just over 52,000 and Thistle finished behind her with nearly 49,000.
Contact Jan Hefler at 856-779-3224 or firstname.lastname@example.org, or follow on Twitter @JanHefler. Read her blog, "Burlco Buzz," at www.philly.com/BurlcoBuzz.