Political science professor Jim Bickerton said even though MacKay is thought of as a strong advocate for the region, there is a lingering belief that it was MacKay who allowed the Progressive Conservative wing of the party to be swallowed up by the Canadian Alliance party in 2003.
As well, Bickerton said MacKay appears to have been kept on a short leash by Prime Minister Stephen Harper.
"There's been a perception that he's been in a situation with a prime minister who hasn't always allowed him to fully express himself," said Bickerton, who teaches at St. Francis Xavier University in Antigonish, N.S. — part of MacKay's riding.
"The perception down here is that Peter really hasn't been able to represent the more Progressive Conservative side of the party in the way that it should have been after the merger."
MacKay's departure, coupled with that of senior cabinet minister John Baird, will hurt the party's electoral fortunes, he said.
"The major kingpins ... are dropping away one by one," said Bickerton. "It certainly weakens the party, especially in Atlantic Canada where they are struggling to begin with."
Federal Liberal candidate Bill Casey, a fellow Nova Scotian who once served in the Tory caucus with MacKay, issued a statement Friday noting all of the Progressive Conservative MPs who were serving at the time of the Alliance merger have since retired, were defeated or left the party.
Without MacKay, the Tories are facing a tough fight in Nova Scotia, where Conservative MPs Gerald Keddy and Greg Kerr have already announced they are not seeking re-election. The only Conservative incumbent running in the province is Scott Armstrong, who will face a challenge from Casey.
In MacKay's riding, residents said the resignation opens the door to considerable political uncertainty.
"It's huge. It's going to be a big difference for people in Central Nova and Pictou County," said Conservative party member Jim Ryan, moments after MacKay's farewell speech at the Museum of Industry in Stellarton, N.S., Friday evening.
"The MacKays have been around for a long time in the political arena here and it'll be interesting to see what kind of future we'll have here without them."
Residents speaking outside a Tim Horton's in Stellarton before MacKay's speech said news of his departure came as a surprise.
"I definitely think he was good for our community," said Wayne McNeil. "I talked to him a couple of times and he seemed like a very, very down-to-earth person."
Marion Marshall made it clear she was not a fan: "I don't care for Peter MacKay and I'm glad to see the end of him ... I think if he's leaving politics he should stay away from politics."
Meanwhile, local politicians praised the former Crown attorney as a hard-working MP who delivered plenty of federal funds to Central Nova since he was first elected in 1997.
Joe Hawes, mayor of the Town of Pictou, was quick to credit MacKay for getting the town a new sewage treatment plant and reviving the local shipyard.
MacKay has held the riding — redrawn in 2004 — since 1997. His father Elmer held the seat from 1971 until 1993, except in 1983-84 when he stepped aside to let Brian Mulroney contest the seat in a byelection.
"It's a real blow," said Hawes. "There's big shoes to fill with his loss."
In an unusual twist, the federal Liberal party confirmed Friday that David MacLeod, the Liberal candidate set to challenge MacKay in his Central Nova riding, formally withdrew from the race Wednesday, citing personal reasons.
MacLeod, a former card-carrying Tory and veterans advocate with 27 years of service in the Canadian Forces, had said he wanted to unseat MacKay because the Conservative government had taken a "hostile" stance towards veterans.
- with files from Tim Callanan