OTTAWA - Bruce Carson's entry into the highest orbit of Ottawa politics began with a casual 2004 job interview in the office of then-Opposition leader Stephen Harper.

The informal session seems typical of the path that Carson -- now embroiled in allegations of illegal lobbying -- followed to an exclusive perch at the centre of power.

It appears a total of five criminal convictions -- two in 1981, three in 1990 -- were no impediment to a savvy and by all accounts highly intelligent policy analyst in a town where who you know is more important than past indiscretions.

Carson first worked with Harper when the future prime minister was a young Reform MP. He would later cross paths with him in helping meld the policies of the Progressive Conservative and Reform parties into something MPs of the newly united right could endorse.

Carson then helped Harper prepare for the leaders' debates in the June 2004 federal election that reduced Paul Martin's Liberals to a minority mandate. As the new Opposition leader, Harper asked Carson to join his team.

"Mr. Harper invited me to come and work for him when we were in opposition. It was an interview in his office, that's all," Carson told The Canadian Press earlier this week. "It was just a meeting in his office."

No security check was required. That changed when Harper's chief of staff, Ian Brodie, asked Carson to be part of the transition team following the Conservative victory in the 2006 election.

Carson told Brodie he had a criminal past. He says Brodie simply advised him to list his convictions on the application form for Secret-level clearance.

Both men say they really don't know what happened next, only that Carson's application passed muster with the security screeners who toil in the Privy Council Office.

"I filled it out and that's the last I saw of it," Carson said.

During the transition, Carson prepared job descriptions for the fortunate 27 chosen to be in Harper's first cabinet. He soon became a fixture in the Prime Minister's Office, serving as policy analyst and problem solver for the next two years.

"I just sort of did whatever needed to be done," Carson recalled. "Ian Brodie and I had a wonderful working relationship where, if problems came up, he and I would work on them.

"It was the best time of my life, working-wise anyway."

Brodie said everyone in the PMO required a Secret clearance.

"There was only a handful of people in the office with Top Secret clearance. When I talk about a handful I mean, probably, five," Brodie said in an interview.

Carson, now 65, said there was never any discussion of a Top Secret clearance for him.

"No, not at all, ever. For the kind of work I was doing that seemed to be sufficient, I guess. I don't know."

One former staffer who worked in the PMO under a different prime minister finds that astonishing.

It is "absolutely implausible" that Carson could have been able to function as a senior official with only a Secret-level clearance, said the one-time staffer, who spoke on condition of anonymity.

The level of scrutiny for a Secret-level clearance is much lower than that for Top Secret.

One insider close to the situation says Secret-level classifications are almost never denied, even for someone with a criminal record-- provided that he makes a clean breast of it.

The insider said Carson's past would not have stood out as something worthy of a red flag and likely wouldn't have been referred directly to the prime minister, his chief of staff, the clerk of the Privy Council or even PCO's national security adviser -- at that time, William Elliott, who is now head of the RCMP.

He said Carson's application was likely cleared by a mid-level official in PCO's security office, which employs "many dozens" of people. Generally, a Secret-level assessment would involve scrutiny of tax records, criminal databases and intelligence files; no field agents would be dispatched to interview neighbours and former employers.

A Top Secret review would be much more onerous, as Derek Burney, a former ambassador to Washington, can attest.

When he first joined the foreign service in 1963, Burney says he was subjected to a rigorous security check that included the FBI showing up to question a half-brother in California, whom he hadn't seen since he was about 13.

He got a "panicked call" from his mother after his half-brother phoned her to find out why the FBI was asking him when he'd last seen Burney and who his friends were.

His brother wondered, "what the hell had I done, robbed a bank or something?"

Burney, who has served as a diplomat, chief of staff to former prime minister Brian Mulroney, head of Harper's transition team and a member of Harper's panel on the future of the Afghan combat mission, has undergone numerous security checks at various times.

He says it can often take months to complete a thorough security assessment. But when a new government is elected, clearances must be done much more quickly, usually in about two weeks, for cabinet ministers and PMO staff.

"I'm assuming what they're doing is vetting for any criminal activity, that's it. That they can do with computers pretty quickly now."

In the real world, job applicants can expect a prospective employer to check their references and speak to former employers. Had anyone checked with Carson's former colleagues at the Library of Parliament, they would presumably have found what The Canadian Press found: Praise for his work but also tales about disappearances from work, dubious excuses for his absences, constant money woes and at least one instance of running up unauthorized charges on a colleague's credit card.

But Burney said the vetting process is not always that structured in the political world.

"In the political world, where a lot of it's based on word-of-mouth reputation -- this guy did a great job for Mr. X or he did a great job for Premier X or whoever -- the vetting would be done through that kind of network."

Moreover, Burney said it would be rare for someone to give a bad review of a prospective staffer's performance.

"There aren't too many people out there who are prepared to throw a dart at somebody on the phone -- unless they're a journalist, of course."

Burney himself didn't hear about Carson's first run-in with the law until some years after the 2006 election. But it seemed to be widely known.

"I had heard -- I wasn't told this by anybody in government -- I'd heard I think from people in Toronto that Bruce had a problem in the 1980s but that he had picked himself up, he had rehabilitated. It was kind a redemption story more than anything else at the time."