PATERSON, N.J. — In a hard-fought race that pitted two Democrats and onetime friends against each other, Representative Bill Pascrell Jr. won the primary in the Ninth Congressional District on Tuesday.

With 90 percent of precincts reporting, Mr. Pascrell had 64 percent of the vote, beating Representative Steve Rothman, with 36 percent, according to The Associated Press.

The Ninth District, in northern New Jersey, is one of a handful of newly shaped Congressional districts across the country with Democrats facing each other because of election maps redrawn after the 2010 census.

The race was exceptional in that one of the candidates, Mr. Rothman, moved in order to challenge a fellow Democrat. And not just any Democrat, but one with whom he had shared dinners and commutes to Washington over 16 years together in Congress.