Once a loser in Columbia, S.C., Republican Senator John McCain desperately wants to avoid repeating the same fate he took accepted in this Southern state’s primary in 2000 - a shellacking that marked the beginning of the end of his first presidential campaign.

The Arizona senator who ran six years ago against party favorite George W. Bush now is positioning himself as the establishment candidate and building a campaign he hopes will ensure victory in South Carolina, mindful that the state’s GOP primary winners have always become the nominee.

“He obviously has learned from that experience,” said the state’s House Speaker Bobby Harrell, a Bush backer in 2000 who so far is unaligned for 2008. “He has been in South Carolina probably more than anybody else over the last year, and has been trying to line up folks who were the key Bush supporters.”

Obstacles, however, stand in McCain’s way, not the least of which are two potential rivals - Massachusetts Gov. Mitt Romney, who has a significant presence in the state and also is aggressively courting high-profile Bush backers, and the popular former New York City Mayor Rudy Giuliani.

More than a year before South Carolina votes in early February 2008, McCain also faces lingering mistrust among some Republicans who voted for Bush in the bitter 2000 primary that raised doubts about the senator’s conservative credentials.

“We’re programmed to hate McCain,” explained Lisa Manini Sox, executive director of the state Senate Republican caucus. She couldn’t pinpoint a single reason for her opposition but cast doubt on whether her mind could be cdhanged.

McCain aides dismiss such comments as the griping of a handful. In fact, his allies insist that many former Bush supporters are rallying behind him as they seek a candidate with a conservative record, a strong chance of winning the general election and solid national security credentials in the post-September 11 world.

“He is the perfect man for his time,” says Henry McMaster, South Carolina’s attorney general and a McCain supporter who was neutral in 2000.

In 2000, McCain - an underdog courting independents and Democrats as well as Republicans - won handily in New Hampshire before losing to Bush by 11 percentage points in South Carolina.

Stunned by the loss up north, Bush’s campaign and the party establishment that supported him went after McCain, who was relatively unknown in the Southern state, raising questions about both the senator’s positions and his character. McCain traded insults in what became a heated battle, and his campaign never recovered.

Since then, McCain has sought to strengthen his standing among Republicans in South Carolina, the state of his close friend, Republican Sen. Lindsey Graham. McCain’s efforts intensified this year in preparation for a run at the White House.

In Washington, he embraced what he dubbed “common sense conservatism,” as his aides in South Carolina hired field organizers, courted grass-roots activists, gave money to local candidates and secured endorsements from elected officials who previously stood with candidate Bush.

Some observers say McCain appears to be building a so-called firewall in an attempt to stop an opponent’s ascent and put him on solid ground should he stumble in the Iowa caucuses, which he skipped in 2000, or the first-in-the-nation New Hampshire primary, where he’ll face stiff challenges from Northeast politicians Giuliani and Romney.

McCain aides are putting down strong organizations in every primary state, and are focusing their efforts in South Carolina on areas that proved deficient for McCain in his first White House run - the ultraconservative swath from Columbia to the northwest. His strongest support comes from the coastal region.

Romney, for his part, has spent months building a grass-roots organization and is expected to announce soon the backing of several elected officials who were Bush allies in 2000, perhaps even Sen. Jim DeMint.

“I’m 250 percent for Romney,” said state Rep. Nikki Randhawa Haley, calling the Massachusetts governor a proven leader who has consistently adhered to core conservative principles. “McCain doesn’t seem to fit the mold for strong conservatives.”

As McCain knows all too well from his defeat six years ago, conservatism counts in South Carolina, home to many members of the religious right.

In 2000, exit polls showed that 65 percent of self-identified conservatives sided with Bush while 29 percent went to McCain. Bush won 69 percent of the Republican vote to McCain’s 26 percent. And, white religious-right voters made up 43 percent of Bush’s vote, compared to 20 percent of McCain’s.

This time, all top-tier hopefuls - John McCain, Rudy Giuliani and Mitt Romney - face challenges in winning over the critical constituency. Support of those voters will be critical in toppling Democrat Hillary Clinton.