By Patricia Zengerle and Richard Cowan
WASHINGTON (Reuters) - Reports that Democratic U.S. Senator Robert Menendez could face corruption charges raised the possibility on Wednesday of Republicans gaining a 55th Senate seat to strengthen their hand in policy fights with Democratic President Barack Obama.
The New Jersey senator is likely to face charges soon related to his dealings with a donor and friend, Florida-based opthalmologist Salomon Melgen, according to a source and media reports on Tuesday.
Menendez aides have declined to comment on what a spokeswoman termed "the latest anonymous and illegal leak."
Menendez, 61, a senior member of the Senate on foreign policy and banking issues, says he has done nothing wrong and has no plans to leave his seat. He has described his relationship with Melgen as a close friendship.
Congressional aides have said that Menendez is expected to keep his seat and fight any charges.
Senate leaders, including some Republicans, have stood behind Menendez for two years amid previous reports he was being investigated, none of which led to any actions against him.
If Menendez were to step down, New Jersey's Republican governor, Chris Christie, would likely appoint a Republican replacement to serve until a special election. That would bring the number of Republicans in the Senate to 55, one seat closer to the 60-seat "super majority" needed to overcome Democrats' procedural roadblocks and advance legislation.
Gaining that incremental edge could mean the difference in a political fight over confirming Loretta Lynch, Obama's nominee to be the next U.S. attorney general, who is opposed by many Republicans. That vote is expected to be very close.
A Menendez resignation could also put Republicans just one vote shy of clearing the way for passage of a human trafficking bill with anti-abortion language, which Democrats have blocked.
The top Democrat on the Senate Foreign Relations Committee, Menendez has criticized Obama administration policy, particularly on Cuba and Iran. Menendez's name, with Republican co-sponsors, is on two bills related to international negotiations over Iran's nuclear program that Obama has threatened to veto.
But he is a strong supporter of the White House on other issues.
Menendez has been a central player in the push for immigration reform, urging a pathway to citizenship for nearly 12 million undocumented residents of the United States.
Menendez is also a senior member of the Senate Banking Committee, which oversees Wall Street regulation, and the tax law-writing Senate Finance Committee.
No laws or constitutional prohibitions would bar Menendez from continuing to cast votes or otherwise work as a senator if he were indicted. There also are no Democratic Party rules that govern whether he would be stripped of any positions in case of an indictment.
Menendez was chairman of the foreign relations panel until January. He spent 13 years in the House of Representatives and was re-elected to his Senate seat in 2012, so his current term will not end until January 2019.
He is Cuban-American and one of the most senior Hispanic politicians in the United States.
The last senator to be indicted, Alaska Republican Ted Stevens, did not resign after he was charged with failing to report gifts and services from an oil company in 2008. Stevens lost his race for re-election that year, and his conviction was dismissed in 2009.
Democrat Harrison Williams was convicted in 1981 for taking bribes and resigned from the Senate in 1982. He held the New Jersey Senate seat now occupied by Menendez.
(Additional reporting by Susan Cornwell and Mark Hosenball; Editing by Kevin Drawbaugh and Grant McCool)