Clinton, the New York senator favored by New Jersey's Democratic establishment, fended off a tough challenge from the Illinois senator that intensified in the final days of the campaign.
With 54 percent of the vote tallied, Clinton topped Obama by 12 percent, or 55 percent to 43 percent.
"It's a great night," said Sen. Robert Menendez, the national co-chair of the Clinton campaign, speaking from the Manhattan Center in New York, where Clinton was scheduled to appear later Tuesday. "This is a good win in New Jersey not withstanding Sen. Obama spent a lot of time there and a lot of resources there."
In early results, Clinton won primaries in Oklahoma, Arkansas, Tennessee, New York and Massachusetts. Obama was the victor in Georgia, Delaware, Alabama and Illinois. Altogether, 22 states were in play but neither candidate was to emerge with enough delegates to secure the nomination.
McCain, whose campaign nearly unraveled six months ago, also put New York, Connecticut, Delaware and Illinois in his column.
McCain, of Arizona, won the state's 52 Republican delegates in a winner-take-all contest. Former Massachusetts Gov. Mitt Romney finished second but picks up no delegates in the winner-take-all contest.
At stake for the Democrats are 107 of 127 total delegates, which will be awarded proportionally.
The other 20 delegates - often referred to as super delegates - are party and elected officials who can support whomever they choose, regardless of Tuesday's outcome.
New Jerseyans who voted Tuesday had their first shot in decades to influence their party's nomination for president because the state moved its primary from June to February.
"You feel like you get to be counted fully," said voter Devon Berry, 34, as he voted in Point Pleasant. "For a state with such a large population as New Jersey to have a say is absolutely a relief for people who care about the direction this country is taking."
Some 4.8 million residents were eligible to vote, and election officials were reporting strong voter turnout.
