By John Whitesides

WASHINGTON (Reuters) - Lindsey Graham isn't everywhere in Washington these days. It just seems that way.

In a politically divided town where compromise can be fleeting and partisanship is the norm, the Republican senator from South Carolina has become a leading voice on nearly every major issue before Congress this year - partly because he has not always followed his party's official stances.

Graham, a conservative who has never been afraid to buck his party and work with Democrats, is one of four Republicans in the "Gang of Eight" group of senators who are trying to craft a deal to revamp the nation's immigration system.

It is an effort that has caused some grumbling in Graham's conservative home state. And it has angered conservative Republicans who vehemently oppose finding ways to provide legal status for most of the estimated 11 million illegal immigrants in the United States.

Graham, 57, also deviated from the party line this week over looming across-the-board spending cuts, saying he would consider raising up to $600 billion in new tax revenue if Democrats accepted significant changes to the Medicare and Medicaid health programs as part of a broader, long-term budget deal.

By suggesting this week that he would be willing to consider more tax increases beyond those that Congress approved on the wealthiest Americans in January, Graham stood virtually alone in his party.

The depth of some Republicans' objections to more tax increases was evident when Republican Senator Ron Johnson of Wisconsin speculated that House of Representatives Speaker John Boehner "would lose his speakership" if he backed such a plan.

At the same time, Graham has delighted some conservatives by joining his close friend, Arizona Senator John McCain, in spearheading criticism of President Barack Obama's administration for its handling of the fatal attack on the U.S. diplomatic compound in Benghazi, Libya, last September 11.

Graham and McCain have cast the attack, which killed U.S. Ambassador Christopher Stevens and three other Americans, as a security failure. They used the episode to delay the Senate confirmation of Chuck Hagel, a former Republican senator from Nebraska, as Obama's defense secretary.

That effort came to an end on Tuesday, when the Senate voted 58-41 to confirm Hagel. Graham voted against Hagel's confirmation.

"I hope he can exceed expectations," Graham told reporters on Tuesday. "I don't dislike Chuck Hagel. I just don't think he's the best guy."

His positions on immigration, government spending and Hagel have amounted to a dizzying series of political twists for Graham as the two-term senator prepares for a re-election campaign next year - and a possible challenge from the conservative Tea Party movement.

"From a political standpoint, Graham has been going left and right at the same time," said William Galston, a senior fellow at the Brookings Institution who was a policy adviser to former President Bill Clinton.

"He is sticking his neck out. South Carolina politics can be pretty unforgiving," Galston said. "But knowing him a little bit, I think he's doing what he believes in both cases. He is serious about policy and governance."

'GOOD CHANCE' FOR IMMIGRATION BILL

Graham and McCain met with Obama at the White House on Tuesday to press their views on immigration and the $85 billion in mandatory spending cuts that are scheduled to take effect at the end of the week.

Obama had called Graham, McCain and another Republican in the Senate group discussing immigration, Florida Senator Marco Rubio, last week.

Graham has been criticized on the immigration issue in a South Carolina radio ad by Numbers USA, a group that supports lower levels of immigration.

The ad, which will begin airing statewide on Wednesday, calls Graham's immigration plan "amnesty and welfare" for illegal immigrants. Continued...