Carnegie, Pa. — Rick Santorum kicked off his Pennsylvania campaign with a leisurely brunch at Bob’s Diner here, wearing an open collar shirt and polishing off a breakfast of eggs and sausage in an appearance seemingly meant to send one message: I’m home.

Republican presidential candidate, former Pennsylvania senator Rick Santorum sits in a booth at Bob's Diner in Carnegie, Pa., Wednesday, April 4, 2012. (Jae C. Hong/Associated Press)

The former senator showed off his local knowledge, ordering a side of bread from Mancini’s, a favorite Pittsburgh-area bakery, and mingled with former constituents from his days as a young western Pennsylvania congressman.

Asked whether Santorum’s home field advantage comes too late in the game to salvage his presidential prospects, a longtime supporter smiled and sipped her coffee. “Same old, same old,” said Meryl Hatton, 61, a retiree from Findlay Township. “They always counted him out every time, but he came through. He doesn’t quit.”

Santorum is counting on the loyalty — and faith — of voters like Hatton to carry him to a victory here on April 24, when Pennsylvania and four other northeastern states choose their Republican nominee for president. His biggest challenge will be to convince voters that he still has a chance despite rival Mitt Romney’s significant lead as well as his momentum after a primary sweep on Tuesday.

A win by Romney here would eliminate remaining doubts that the Republican Party has accepted his primacy in the nomination fight. It would also deliver a crushing blow to Santorum’s presidential prospects — and his reputation.

Santorum brushed off questions from reporters about whether he was imperiling any future run for office by competing in his home state, where he famously lost his Senate seat in 2006 by 18 points. “Next time?” he joked. “You’re going to have to ask my wife about a next time.”

He said the environment in Pennsylvania and the country had become more friendly to conservatives in the past six years and predicted he will win the state, despite what he expected will be an onslaught of negative ads from Romney and his backers. In another indication that he was not planning to bow out of the race, he said he looks forward to May, when Texas and a number of southern states — where he would be expected to have an advantage — hold their primaries.

“The people of Pennsylvania know me,” he said. “All the negative attacks are I think going to fall on a lot of deaf ears here. We’ve got a strong base of support here and we’re going to work very very hard and then we’re going to get into May, and May is looking very very good.”