WASHINGTON - Sen. Robert Menendez (D., N.J.) was indicted on 14 counts of federal corruption Wednesday, accused of using his office to help a donor who had lavished him with gifts, including numerous flights on a private jet, a stay in a five-star Paris hotel, and vacations at a luxury resort in the Dominican Republic.

In exchange, Menendez, 61, allegedly pressed high-ranking federal officials on issues important to the business and personal affairs of the donor, South Florida eye doctor Salomon Melgen.

A defiant Menendez said Wednesday that he has always followed the law and vowed to be vindicated.

"I am not going anywhere," Menendez told reporters and supporters in Newark. "I am angry and ready to fight. Today contradicts my public-service career in my entire life."

Menendez is due in court Thursday.

The accusations cast a shadow over a 22-year member of Congress who has emerged as a leading voice on international policy and an advocate for Hispanics nationwide.

There was one immediate consequence: Menendez stepped down as the top Democrat on the Senate Foreign Relations Committee, a position that had given him a place on the global stage. In a letter to the top Senate Democrat, Harry Reid, Menendez said the move was "in the best interests of the committee, my colleagues, and the Senate."

Menendez is accused of aiding Melgen in a dispute over $8.9 million in Medicare billing - submitted improperly, according to federal officials - in a fight over a lucrative business deal in the Dominican Republic, and in requests by three of Melgen's girlfriends' for tourist or student visas as they traveled from Brazil, the Dominican Republic, and Ukraine.

Menendez and Melgen, of West Palm Beach, Fla., were charged with conspiracy, bribery, honest-services fraud, and violating the travel act. Menendez also was charged with making false statements.

Corruption "corrodes the public trust and weakens our democratic system," Assistant Attorney General Leslie R. Caldwell said in a news release.

Menendez pushed back at a raucous news conference. "Viva Bob!" a supporter shouted.

Melgen's attorneys declined to comment, the Miami Herald reported.

The charges against Menendez have been long expected, and the senator lined up an outpouring of support.

One of the country's leading Hispanic advocates - Frank Sharry, of America's Voice - and Democrats across New Jersey blasted out statements backing Menendez, as did a Twitter account, I Stand With Bob.

A website by the same name sprang up, soliciting donations to help him.

"Senator Menendez has never wavered in his commitment to the people of New Jersey," Sen. Cory A. Booker (D., N.J.) said in a news release. "I won't waver in my commitment to stand alongside my senior senator to serve our great state."

Most Republicans held their fire, though conservative groups called for Menendez to resign, and ethics watchdogs decried the picture painted in the indictment.

Menendez "cannot represent the people of New Jersey," said Phil Kerpen, president of the conservative group American Commitment, which has a petition calling for him to step down.

Meredith McGehee, policy director of the nonpartisan Campaign Legal Center, said "the kind of cronyism" in the case "confirms what most Americans believe about Washington."

Menendez is just the 12th sitting U.S. senator to be indicted and the first since Ted Stevens (R., Alaska) in 2008. Stevens was convicted but then cleared due to misconduct by prosecutors.

Another New Jersey senator, Democrat Robert Torricelli, resigned in 2002 after he accepted gifts from a donor. He did not face criminal charges, only a reprimand from the Senate ethics committee and a likely election loss.

Menendez does not face voters again until 2018, giving him time to fight the charges.

The indictment lays out numerous trips Menendez took to Melgen's Spanish-style villa at a Dominican resort and a three-night stay in an executive suite at the Park Hyatt Paris-Vendome, among other gifts. The Paris stay in 2010 was valued at $4,934, but Melgen paid with 649,611 American Express points, the indictment says.

Menendez failed to reveal the various gifts on financial disclosure forms filed in 2006, 2007, 2008, and 2010, authorities say.

Melgen, his business, and family also gave more than $700,000 to committees backing Menendez's 2012 reelection.

Meanwhile, Menendez and his aides, often armed with talking points from the doctor's lobbyist, advocated for Melgen in Washington, prosecutors say.

Menendez met with a cabinet official, then-Secretary of Health and Human Services Kathleen Sebelius, and pressed an ambassador, heads of executive agencies, and other senior officials, according to the indictment. He arranged a meeting between Melgen and then-Sen. Tom Harkin (D., Iowa) in 2011.

Menendez and his aides questioned federal policies that led to Melgen being ordered to give back $8.9 million in Medicare payments for treatments he had given at his eye practice, prosecutors say. Menendez also urged officials to help in a dispute over a contract that a Melgen-backed company had to provide security screening equipment at Dominican ports.

Menendez threatened to call a hearing on the issue, an assistant secretary of state wrote in an e-mail included in the indictment.

Along the way Melgen fired e-mails to Menendez staffers, and Menendez urged aides to act fast on his friend's requests, the indictment shows.

In January 2013, shortly before FBI agents raided Melgen's Florida office, Menendez paid back $58,500 for two 2010 trips on Melgen's private plane. His campaign later paid $11,250 for a third undisclosed flight, in 2011.

Menendez has said the flights "fell through the cracks" during a busy time, and aides have said he wasn't advocating for Melgen, but raising policy concerns.

One challenge for prosecutors will be proving that the gifts were tied to official acts, not just exchanges between friends. Menendez has stressed his more than two-decade relationship with Melgen, saying in March that they exchange gifts "just as friends do."

Menendez is known as a fighter who is expected to tenaciously cling to his seat. But he is one of the least-wealthy members of the Senate, so a long trial could test his resources.

He had raised about $867,000 for a legal-defense fund by the end of 2014. He spent about $763,000, according to public filings.

The criminal charges will bring into full view a long-running and often shadowy saga that began in 2012 with a mysterious e-mailer making unsubstantiated accusations of Menendez's having trysts with Dominican prostitutes.

The accusation, picked up on a conservative website, quickly fell apart but led to a focus on the senator's ties to Melgen.

Along the way there have been accusations from Menendez allies that the stories were the product of Cuban enemies, right-wing blogs, and (according to some Republicans) the Obama administration seeking to punish a senator who has defied the president on negotiations with Iran - which reached a critical deadline this week.

Menendez said the investigation began with "false allegations by those who have a political motive to silence me."

After years of whispers, he now has to formally respond.