By CNN Political Unit
(CNN) -- New Jersey's largest newspaper had some tough words Sunday for Sen. Bob Menendez as he faces allegations of improper travel and parties with prostitutes. The same paper endorsed the senator's bid for re-election three months ago.
An editorial in the Newark-based Star-Ledger said the accusations raised "serious doubts about his fitness to serve as Chairman of the Foreign Relations Committee" and argued he "needs to break his silence and explain himself."
The chairmanship had been held by former Sen. John Kerry, who was sworn in as secretary of state on Friday. Menendez is set to take over the position this week.
Menendez has been in the spotlight as scrutiny escalates over his relationship with a generous donor whose plane he took to the Dominican Republic and who has business ties in the Caribbean nation.
The scandal first emerged shortly before Election Day last fall, when a conservative online publication cited three unidentified sources who claimed the senator had flown on private planes to the Caribbean and during the trip had sex parties with prostitutes.
In response to a question Thursday from CNN regarding whether he broke finance laws, Menendez deferred to his office but added "these are nameless, faceless, anonymous allegations. You should find out from them."
The Star-Ledger didn't put much stock in the prostitute claims, saying the allegations have no credible evidence and have "all the markings of a dirty trick."
But it raised questions about the plane trips, which Menendez took in 2010 but didn't pay for until January 4 of this year - a gap that his spokeswoman, Patricia Enright, described as an "oversight." His office said Menendez paid $58,500 from his personal funds.
The Star-Ledger editorial board, however, didn't buy that it was simply an "oversight."
"Why would anyone remember something so routine and mundane as a rich guy whisking you off to an exotic vacation in the Caribbean in a private jet? If the senator has no better explanation, he will richly deserve the reprimand the full Senate will no doubt impose on him," the editorial stated.
FBI agents searched and removed material Wednesday from the office of the donor, Florida ophthalmologist Salomon Melgen, sparking renewed attention to the scandal.
An FBI spokesman in Florida has confirmed there was "law enforcement activity" at the location, but did not elaborate or mention any person specifically.
Another issue has to do with whether Menendez advocated on Capitol Hill on behalf of ICSSI - a port security company in which Melgen has a stake. The company had a contract to screen cargo that went through Dominican ports, but Menendez argued last July during a Senate subcommittee hearing that Dominican authorities didn't want to "live by" the contract.
"Why, then, did Menendez put pressure on officials at the State Department and Commerce Department over the contract during a hearing? Was he using his position on the Foreign Affairs Committee to advocate for his friend's business interests? Keep in mind, Melgen was not a constituent; he was a money man who had given generously to Menendez," the editorial sated.
"This is tawdry stuff," it continued. "For all his talents, Menendez seems to have behaved like a slippery Hudson County pol. We are eager to hear his explanation."
Meanwhile, the Senate's top Democrat, Majority Leader Harry Reid, came to his colleague's defense on Sunday, reiterating he has full confidence in Menendez.
"He was a leader in the House. He's been a leader in the Senate. He's chairman of that committee. He'll do a wonderful job. And he's also an integral part of what we do with immigration reform. So, I have the utmost confidence in him," Reid said on ABC's "This Week." "I have confidence he did nothing wrong. But that's what investigations are all about."
CNN's Ashley Killough, Steve Brusk, Greg Clary, Jim Acosta, Greg Botelho, Adriana Hauser, Susan Candiotti and Ross Levitt contributed to this report.