WASHINGTON - Sen. Bob Menendez (D., N.J.) was indicted on 14 counts of federal corruption charges 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 that the charges come from people "with a political motive to silence me."

He vowed to be vindicated.

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

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

Menendez, due in court to formally face the charges Thursday, is expected to step down from his position as the top Democrat on the Senate Foreign Relations Committee, according to National Journal, costing him a job that had given him a place on the global stage.

Menendez is accused of aiding Melgen in an $8.9 million Medicare billing dispute, a fight over a lucrative business deal in the Dominican and helping as three of Melgen's girlfriends sought tourist or student visas from Brazil, the Dominican and Ukraine.

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

"Government corruption - at any level of elected office - 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!" 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, funded by Menendez's campaign and soliciting donations to help him.

"Senator Menendez has never wavered in his commitment to the people of New Jersey," Sen. Cory 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 an online 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, was pushed to resign in 2002 after he also accepted gifts from a donor. He did not face criminal charges, only a reprimand from the Senate Ethics Committee and a likely election loss.

Among other gifts, 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 five-star in Park Hyatt Paris-Vendome. That stay in 2010 was valued at $4,934, though Melgen paid with 649,611 American Express points, the indictment says.

Prosecutors also pointed to more than $700,000 Melgen, his business and family gave to political committees backing Menendez's 2012 re-election.

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

Menendez met with a cabinet official, then-Secretary of Health and Human Services Kathleen Sebelius, at one point, and also pressed an ambassador, heads of executive agencies and other senior officials. And 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. Menendez also urged federal officials to act in a dispute over a contract 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 repeatedly fired emails to Menendez staffers and the aides were quick to respond.

In January 2013, shortly before FBI agents raided Melgen's West Palm Beach office, Menendez wrote a $58,500 check for two 2010 trips on Melgen's private plane. He later had his campaign pay $11,250 for a third undisclosed flight, in 2011.

Menendez has expressed "regret" that the flights "fell through the cracks" during a time of busy travel.

One critical challenge for prosecutors will be proving that the gifts were not just exchanges between two friends and were, in fact, tied to official favors.

Menendez has stressed his long relationship wiht 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 Senate seat. The son of Cuban immigrants, he first climbed to power in Hudson County, one of New Jersey's most gritty political arenas, and has broken barriers for Hispanics at nearly every stage of his career.

But he is one of the least wealthy members of the Senate, so a long trial could test his resources.

Menendez had raised about $867,000 for a legal defense fund by the end of 2014, but spent about $763,000, according to filings with the Internal Revenue Service.

The criminal charges will bring into full view a long-running and often shadowy saga that began with unsubstantiated accusations of Menendez having trysts with Dominican prostitutes and turned to a focus on the senator taking official actions that could have helped Melgen's businesses and finances.

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 strongly defied the president on U.S. relations with Cuba and negotiations with Iran - which reached a critical deadline just before the indictment was announced.

Now, after months of whispers, Menendez will have to formally respond to detailed accusations.

@JonathanTamari

Staff writer Andrew Seidman contributed to this report.