By Jeff Mason and Richard Cowan

WASHINGTON (Reuters) - Nevada Governor Brian Sandoval, a Republican and former federal judge, is among candidates being considered by President Barack Obama for appointment to the Supreme Court, a source close to the process said on Wednesday, as Obama sought to overcome Senate Republican resistance to any nominee.

Sandoval, a 52-year-old Mexican-American, is considered a moderate Republican, particularly on social issues. He supports abortion rights and abandoned the state's legal defense of a same-sex marriage ban before the U.S. Supreme Court ruled that such bans were unconstitutional.

Sandoval has supported gun rights as governor, which could prompt concerns from gun-control advocates. He was appointed as a federal judge by Republican George W. Bush, Obama's predecessor, before being elected governor in 2010.

An intense political fight has erupted since the Feb. 13 death of long-serving conservative Justice Antonin Scalia created an opening on the Supreme Court bench. Republicans are maneuvering to foil Obama's ability to choose a replacement who could tilt the court to the left for the first time in decades.

The Republican-led Senate must confirm any high court nominee and Majority Leader Mitch McConnell announced on Tuesday that the chamber will not hold hearings or vote on any Supreme Court nominee until after the next president takes office in January.

Sandoval met on Monday in the U.S. Capitol for about 30 minutes with Senate Democratic leader Harry Reid of Nevada. Reid asked the governor whether he would be interested in being considered for the high court job, according to the source, who asked not to be identified.

"He said he was interested," the source said of Sandoval, adding that "a number of people are being checked out" for the job.

Sandoval, who was in Washington for a National Governors’ Association meeting, also spoke to Reid by telephone last week, the source said.

Sandoval opposed Obama's healthcare law known as Obamacare, but opted to expand his state's Medicaid health insurance program for the poor under the law, breaking from a number of Republican governors who refused to do so.

He also expressed support for bipartisan immigration legislation that passed the Senate in 2013 before dying in the House thanks to Republican opposition.

In 2013, Sandoval vetoed legislation to require background checks on all gun sales in Nevada. Last year, he signed a law backed by the National Rifle Association that, among other things, expanded the defenses for justifiable homicide and repealed a local ordinance in Clark County, where Las Vegas is located, that required registration of handguns.

'WORTHY TO SIT'

Obama vowed on Wednesday to move ahead with a nominee and said Republicans would risk public ire if they blocked a qualified candidate for political motives, as well as diminishing the credibility of the high court.

Obama said he expected the Senate Judiciary Committee to extend his nominee the courtesy of a hearing and then vote on whether he or she is qualified.

"In the meantime, the American people are going to have the ability to gauge whether the person I've nominated is well within the mainstream, is a good jurist, is somebody who's worthy to sit on the Supreme Court," Obama told reporters in the Oval Office.

"I think it will be very difficult for Mr. McConnell to explain how, if the public concludes that this person's very well qualified, that the Senate should stand in the way simply for political reasons."

The president said he understood the political predicament Republicans faced and said he had expressed sympathy in calls to their leaders. He said they were sheepish in their arguments that a nominee should not be confirmed until next year and predicted their posture would change.

"I think the situation may evolve over time. I don't expect Mitch McConnell to say that is the case today," he said.

In a post on the independent SCOTUSblog.com website, Obama listed his criteria for a nominee including "an independent mind, rigorous intellect, impeccable credentials and a record of excellence and integrity."

Liberals vowed to pressure Senate Republicans into considering an Obama nomination this year, with several groups delivering to the Senate boxes of what they said contained 1.3 million signatures from citizens demanding that a confirmation process go forward after the president announces his pick.

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