"This fund is necessitated by, and intended to defray, legal expenses and related expenses I incur and am responsible for in connection with legal inquiries, including by the Select Committee on Ethics of the United States Senate and the United States Department of Justice, involving allegations of violations of the Standing Rules and standards of the Senate and Federal Statutes," the affidavit reads.
A Friday campaign filing shows how legal expenses have taxed Menendez's campaign account. He paid $489,000 in legal fees related to the investigations in 2013, while taking in $317,421 in campaign contributions. (He does not have to run again until 2018.)
The report also shows that on Dec. 18, Menendez's campaign repaid donor Salomon Melgen $11,250, nearly three years after a Jan. 30, 2011, flight on Melgen's plane.
"Due to an oversight, the campaign did not reimburse Dr. Melgen for the cost of that flight at the time," Menendez spokeswoman Patricia Enright wrote in a statement. "When that oversight was discovered at the end of 2013, Sen. Menendez directed his campaign to immediately reimburse Dr. Melgen."
Multiple news outlets - prominently the Washington Post and the Miami Herald - have reported that there is a federal grand jury investigation of Menendez, and the Post has reported an ethics committee inquiry.
Those reports had not been officially confirmed, though they had never been denied by Menendez's office.
"We have always said we will welcome any review into the senator's actions, and believe they have been appropriate and believe the facts will confirm that," Enright said Friday.
Menendez early last year repaid Melgen $58,500 for two 2010 flights on the donor's plane after the trips became the subject of an ethics complaint. Menendez paid for those personally because they were not related to official business.
The newly revealed flight, from Florida to New Jersey, was related to a campaign event, so it was repaid by Menendez's campaign fund.
The federal investigation of the senator is believed to center on his relationship with Melgen. Menendez has written government officials on behalf of Melgen in disputes over Medicare billing and a contract for port security in the Dominican Republic.
Melgen and his family have donated more than $1 million to Menendez and committees that have supported him.
After an FBI raid on Melgen's office in early 2013, Menendez spokesman Paul Brubaker told The Inquirer that an "extensive review" had turned up the two unpaid-for flights and that there were "no outstanding issues with his travel."
Enright said Friday reviews of Menendez's travel had "been ongoing."
The legal fund will allow Menendez to collect up to $10,000 per year from each donor to help pay legal expenses related to his official work.
Menendez can also use his campaign account for his defense, but donors can only give that fund a maximum of $5,200 per election cycle, every six years for a senator.
The defense fund cannot collect money from lobbyists, corporations, unions, foreign nationals, or the principal campaign committees of any fellow lawmaker, said Rob Walker, a lawyer at Wiley Rein and former chief counsel to the House and Senate ethics committees.
Menendez's campaign paid $250,000 to the law firm of McDermott, Will & Emery over the last three months of the year, in addition to $82,869 paid in June.
An additional $156,240 was paid to Perkins Coie to represent the campaign fund in relation to the inquiries. That amount was also covered by the campaign account.