John Adler defeated Republican Chris Myers in the southern New Jersey's 3rd District.
But incumbent Republican Scott Garrett held off a strong challenge in the 5th District of northern New Jersey from Dennis Shulman, a blind ordained rabbi. And Republican state Sen. Leonard Lance defeated Democrat Linda Stender, a state assemblywoman, for a seat being vacated by Rep. Mike Ferguson in central New Jersey's 7th District.
"It is now time to come together as a nation, putting country ahead of party," said Lance, who promised his service in Washington would be guided by "moderation and common sense."
Myers, the mayor of Medford, did not fare as well.
"It's a bad year to be a Republican," he said. "We ran a good, hard race. Who knows what two years will bring from now?"
Adler's victory gave Democrats an 8-5 margin in New Jersey's congressional delegation. The seat he won is being vacated by Republican Jim Saxton, who is retiring.
Obama had maintained a double-digit lead in the polls for weeks over Republican John McCain in one of most Democratic-leaning states on the electoral map - one that has not gone Republican in a presidential election in 20 years.
In the Senate race, Lautenberg shrugged off a challenge by Republican Dick Zimmer, a former congressman who had trouble establishing name recognition in an underfunded campaign.
Lautenberg, who is 84 and would be 90 by the end of his next term, was able to overcome voter misgivings about his advanced age.
"The country is demanding a drastic change from the policies of the last eight years," Lautenberg said. "Working with President Barack Obama, we will deliver for our country. Times are tough, but I promise you, brighter days are ahead for all of us."
His Senate colleague Robert Menendez, a fellow Democrat, said Obama's victory will inspire millions.
"It sends a message to the world and to every child here in America that it doesn't matter the color of your skin or the happenstance of where you were born, if you are willing to work hard and you have good ideas, America is willing to reward you," Menendez said. "This is a country of opportunity."
Makhan Taylor, a 27-year-old accountant from Perth Amboy, rejoiced at Obama's historic victory.
"An Obama presidency gives me hope that there will be a change," she said. "We're definitely going a different route here after eight yards of Republicans in the White House. It's time now to give Barack Obama a chance to show what he can do."
In Newark, resident blared car horns and whooped in celebration as new outlets declared the Obama victory at 11 p.m.
Voting problems were widespread but not systemic across New Jersey on Tuesday. Problems ran from early morning voting machine difficulties in Willingboro and Essex County to voters being turned away because their names were not in the books listing registered voters.
Attorneys for the state Public Advocate handled more than 250 voting appeals by midday and had prevailed in 90 percent of them.
A surge in new registrations - 631,000 since January alone - pushed the state's voter rolls to a record 5.4 million, and political experts predicted a turnout that might surpass the 83 percent of New Jersey voters who turned out for presidential races in 1940, 1972 and 1992.
Voters decided two statewide ballot questions. A measure to require voter approval in most cases before the state borrows money was approved. The other, to allow the appointment of municipal judges who serve multiple communities to be made without the consent of the state Senate, was rejected by voters.
