Robert Menendez’s education in political corruption came unusually early. In 1982, he turned against his mentor, Mayor William V. Musto of Union City, N.J., the popular leader of their gritty hometown.
Mr. Menendez took the witness stand and testified that city officials had pocketed kickbacks on construction projects, helping to put a man widely seen as his father figure behind bars. Mr. Menendez, then 28, wore a bulletproof vest for a month.
The episode, which Mr. Menendez has used to cast himself as a gutsy Democratic reformer, helped fuel his remarkable rise from a Jersey tenement to the pinnacles of power in Washington as the state’s senior senator. The son of Cuban immigrants, Mr. Menendez broke barriers for Latinos and has used his perch as chairman of the Senate Foreign Relations Committee to influence presidents and prime ministers.
But those who have closely followed his career say the years he spent enmeshed in Mr. Musto’s machine also set the tone for another, more sinister undercurrent that now threatens to swallow it — one in which Mr. Menendez became a power broker himself whose own close ties to moneyed interests have repeatedly attracted the scrutiny of federal prosecutors.
The explosive bribery charges he now faces accuse the senator and his wife of taking hundreds of thousands of dollars in bribes in exchange for helping increase U.S. assistance to Egypt and trying to throttle a pair of criminal investigations involving New Jersey businessmen. Investigators who searched their suburban home found piles of cash squirreled away, gold bars, and what they described as an ill-gotten Mercedes-Benz.
Interviews with nearly two dozen New Jersey political figures who worked with, watched and fought him, as well as a review of court records stretching back two decades, paint a complicated portrait of a man who has been both a pathbreaking legislator of unusual intelligence and a vindictive politician with a propensity for accepting lavish gifts he could never have afforded on a government salary.
As a measure of how damning the indictment appears, no one — not even a longtime ally recommended by Mr. Menendez’s office — agreed to publicly defend him on the conduct described by prosecutors.
“What we are witnessing is a pattern that developed early and just spun out of control,” said Robert Torricelli, a former Democratic senator from New Jersey who served alongside Mr. Menendez in Washington. “People don’t often change. In a lot of ways, Bob Menendez is still a Union City commissioner in the late 1970s.”