MECHANICSBURG, Pa. — Rick Santorum is back on familiar ground, seeking redemption and a lifeline for his presidential candidacy in the state that rejected him almost six years ago.

The former senator from Pennsylvania has resurrected his career after a shattering 2006 reelection defeat. Dismissed as a hopeless long shot when his presidential run began, he’ll finish no worse than second for the Republican nomination. At 53, he’s one of the nation’s leading social conservatives, and his long-range future has never looked brighter.

But as he resumes a do-or-die Pennsylvania primary effort this week, he’ll need all his local connections and considerable campaign talents to survive what could be the final showdown of the 2012 GOP contest. Polls show him with a small lead over Mitt Romney, who’d like nothing more than to finish off his main rival in the April 24 election.

After a day spent traversing the state’s steeply eroded ridges, studded with redbud blossoms and trees just greening up, Santorum expressed satisfaction at returning to “familiar territory, where I can say, ‘No, no, there’s a shorter way to get there’ to the drivers.”

He’s all but said that a primary loss would end his candidacy. “We have to win here,” he told reporters during a stop at Bob’s Diner in Carnegie, a Pittsburgh suburb he represented as a young congressman in the early 1990s.

Romney’s nonstop attack ads have erased Santorum’s initial advantage in some previous primaries, particularly in the larger, more diverse states that closely resemble Pennsylvania, with plenty of moderate suburban voters and fewer evangelical Christians. But Santorum said that “people in Pennsylvania know me. All of the negative attacks, I think, are going to fall on a lot of deaf ears here.”

Home-state familiarity also cuts against him. His warts are widely known, and success elsewhere hasn’t altered his complicated relationship with state politicians — relatively few actively support him — and with ordinary Republican voters.

“There are people here who like him and people here who hate him,” said Barth Levy, a 54-year-old architect from Zelienople, who attended a Santorum rally in Mars. “I’ve been impressed by his ability to soldier on. He’s far surpassed any expectations anybody had.” The Santorum fan also acknowledged that the GOP race “is kind of over.”

Yet growing calls for his surrender seem to have stiffened Santorum’s determination to risk a second straight home-state defeat. There was a sharp edge to his voice when he complained to reporters at a bowling alley in Mechanicsburg that he’d been asked “every five minutes, ‘When are you going to get out of the race?’ for the last week.”

His stubborn streak contributed to the 2006 general election defeat by more than 17 percentage points, one of the worst losses in decades for a Senate incumbent anywhere in the country. Even supporters say that he would have fared better if he hadn’t come across as arrogant and overly combative.

Santorum’s prickly personality is well-known in western Pennsylvania, where he grew up on the Department of Veterans Affairs’ 88-acre campus in working-class Butler — his father was a psychologist, his mother a nurse — and began his rise in politics.

“You either agree with him or you’re wrong. He has no interest in your point of view. He’s very dogmatic,” said Pittsburgh businessman Jim Roddey, chairman of the Allegheny County GOP. The former Santorum backer has endorsed Romney for president.

State campaign coordinator Brian Nutt said “thousands” of supporters would be knocking on doors over the next two weeks, and Santorum would visit at least 25 or 30 of the state’s 67 counties. An in-person effort may be particularly important if Roddey is right that Santorum has grown “a little out of touch with his base” after many years as a northern Virginia resident.

Bob Hillen, a Pittsburgh chairman of Santorum’s 2000 Senate reelection campaign, said that Santorum “lost his way a little bit” during his final years in Congress, when he seemed more interested in his status as the No. 3 Republican in the Senate leadership than in representing Pennsylvania. That was one reason that Hillen initially supported outsider Herman Cain for president, switching to Santorum only after Cain dropped out.

Hillen, a 54-year-old house painter, can still remember confronting Santorum over the senator’s 2004 endorsement of former liberal Republican Sen. Arlen Specter against conservative primary challenger Patrick J. Toomey, now the state’s junior senator.

“I told him, ‘What the hell are you doing?’ ” said Hillen, who couldn’t swallow Santorum’s explanation that it was all about facilitating the confirmation of President George W. Bush’s conservative judicial picks. “It makes sense now,” he said, “especially with the healthcare issue hitting the Supreme Court.”

Lingering conservative resentment over the Specter endorsement could surface again this month.

“He made a mistake with Sen. Specter that cost him dearly and it could very well cost him again,” said Mitch Cooper, the Republican sheriff of Blair County in conservative central Pennsylvania, who is undecided in the presidential race.

Santorum’s chances will turn on his ability to offset Romney’s strength in the moderate Philadelphia suburbs by running up large margins in the rest of the state.

At Santorum’s first central Pennsylvania campaign stop, a rally last week at the courthouse in Hollidaysburg, he reached out to social conservatives and blue-collar voters, reminiscing about his first kill as a deer hunter and his grandfather’s work in nearby coal mines.

Then he turned to an incendiary remark Barack Obama made during his 2008 campaign, at a fundraiser in Northern California, about the hard-pressed residents of small Pennsylvania towns. (“They get bitter. They cling to guns or religion,” Obama said.)

“You’re damn right we do!” Santorum declared, to applause. “We cling to our faith. We cling to the rights that are God-given, that are guaranteed under our Constitution, including the right to protect ourselves and those we love with the 2nd Amendment, an individual right to bear arms.”

He went on to attack Romney’s past support for gun control. Playing up cultural contrasts with the former Massachusetts governor is a central theme of Santorum’s return engagement with Pennsylvania voters. Adopting the image of a scrappy outsider, he described himself to reporters as someone who “clawed his way up through the political process, never being anybody’s favorite, always being the underdog, always being someone that was discounted. I think folks in Pennsylvania for a long time have admired that story and can relate to that story, and I think they will again in this election cycle.”

paul.west@latimes.com