The Harper-era cabinet minister told CBC News he's proud to report that as of June, his campaign has paid off "every penny" it owed. He acknowledged it was a struggle.

"It was not easy, to say the least. It was a very heavy burden to carry after the result of the leadership. To be informed that we were that much in debt was a shock to me," he said.

MacKay's leadership race was one of the first held under a federal election law that gives candidates three years to raise enough donations to pay off campaign debts. If they don't, the consequences can include fines and even jail time.

MacKay said he faced a number of hurdles as he worked to pay off the debt, including the pandemic and having to compete for donations with provincial elections, a federal election and the 2022 Conservative leadership race.

MacKay said the fact that he's no longer engaged in politics also played a role.

"It's extremely difficult to raise money when you're not in the game, so to speak," he said. "You're not in elected office, you're not running for anything at that point. You're trying to clean up past debt."

MacKay considered running for office again in late 2020 after Erin O'Toole won the leadership. He ultimately announced he had made what he called a "difficult" decision not to run again in order to focus on his family and his full-time job as a lawyer.

U.S. Secretary of State Condoleezza Rice chats with Peter MacKay, foreign affairs minister at the time, before a meeting in Ottawa on February 23, 2007. (Fred Chartrand/Canadian Press)

MacKay turned for fundraising help to some famous figures in politics — including former prime ministers Stephen Harper and Brian Mulroney, Conservative Leader Pierre Poilievre, Alberta Premier Danielle Smith, Nova Scotia Premier Tim Houston and former U.S. secretary of state Condoleezza Rice. He even reached out to celebrated country singer George Canyon.

MacKay credits his former campaign team and the donors themselves for helping him wipe away the debt.

Still, it's clear the former cabinet minister — once widely viewed as the front-runner for the Conservative leadership — has mixed feelings about his last foray into politics.

MacKay 'disappointed' by leadership outcome

He said the "largest factor" behind the debt his campaign racked up was the decision by the Conservatives' leadership committee to pause the race in March 2020 and extend the deadline to sign up new members due to the pandemic.

"They sort of dropped that on us late in the third period," he said. "If I could use the hockey analogy, being told, 'OK, you know, the game is almost over. Oh, sorry, did we mention we're going to play a fourth period?'"

He later leaned on another sports metaphor.

"Moving the goalposts is one thing," he said. "Moving them to another stadium in a different time zone? I think it affected the outcome, sure."

MacKay would not say whether he feels that decision cost him the leadership.

"I don't want to be that guy who complains about the outcome," he said. "I'll leave that for others."

MacKay watches the announcement of his party's new leader with his wife Nazanin Afshin-Jam MacKay and son Kian in Ottawa on Aug. 23, 2020. (Justin Tang/The Canadian Press)

During his conversations with CBC News, MacKay himself asked whether he sounded bitter and insisted that's not the impression he wants to leave.

"I'm really not bitter," he said. "'Disappointed' is the word."

One of the co-chairs of the committee that made the decision to extend the race said there was no real alternative at the time. Party officials reported they were unable to stick to the original plan because of the challenges thrown up by the pandemic, said Dan Nowlan.

"It's disappointing that we had to extend the timeline but, honestly, we didn't have a choice," he said.

Nowlan said the committee tried to ensure the race wasn't extended one day longer than necessary.

MacKay says O'Toole's team never reached out

MacKay did say he was let down by the way he was treated after losing.

MacKay pointed to the way Brian Mulroney reached out to rival Joe Clark and his team after winning the Progressive Conservative leadership in 1983.

"That kind of magnanimity is critical. It's the ... glue that keeps the party together when you do that," he said. "When you don't, it's more frayed edges and the rot can then seep into the deck of the party."

There was no similar outreach after Erin O'Toole beat him in the 2020 leadership race, said MacKay.

But O'Toole's campaign manager for the leadership race said the suggestion the campaign never reached out to MacKay is "completely false."

O'Toole's team had "many conversations" with MacKay and told him he would be welcome to run as a candidate, said Fred DeLorey.

The campaign also helped MacKay with his fundraising efforts, he added.

"We all wish Peter MacKay nothing but the best and hope he finds peace with this loss," said DeLorey.

Despite the bruises and scars lingering from that race, MacKay said he doesn't regret his decision to run.

"No … I [saw] a potential opportunity to bring our party back to government," he said.

MacKay said there's a silver lining to his leadership loss: he's been able to spend much more time with his wife and three young children. He likely wouldn't have met his wife without his time in Ottawa, he added.

MacKay said he's focused on moving forward, not on whether he missed a shot at becoming prime minister.

"Do I regret never having had a chance to run for the top job?" he said. "I'm not going to let that be something that defines me."