Today, Zajdel is facing a list of criminal charges after his arrest Monday as part of Quebec's ongoing anti-corruption crackdown.
The Conservative election candidate was picked up along with Montreal Mayor Michael Applebaum and was slapped with five charges from acts allegedly committed back in his days as a municipal councillor.
The charges include breach of trust, fraud, bribery and corruption linked to alleged activities that took place between Jan. 1, 2007, and Dec. 31, 2008.
Zajdel, 57, narrowly lost to Liberal incumbent Irwin Cotler in the 2011 election and, after the vote, was put on the payroll in a minister's office to work on ethnic outreach.
Cotler had raised concerns that Zajdel was earning a government paycheque while trying to perform MP-like duties in his Montreal riding.
He had described Zajdel as a "shadow MP" in his riding of Mount Royal, a complaint that followed reports of mysterious phone calls to his constituents that suggested the former justice minister, then 71 years old, was on the verge of retiring.
Zajdel abruptly resigned from that federal job last spring.
A couple of weeks before he quit, Zajdel had been part of Harper's entourage during the prime minister's visit to Montreal, which included a March 2012 public event just a few hundred metres from the border of Cotler's riding.
Harper and Zajdel also made an appearance together later that day at an Old Montreal pub where they met with party supporters.
The Harper government distanced itself from Zajdel on Monday.
It confirmed that Zajdel worked in the office of Heritage Minister James Moore from October 2011 to March 2012 as a liaison with Montreal's cultural communities.
But the government and the Conservative party both said that none of the allegations against Zajdel were known at the time despite standard background checks.
Moore, meanwhile, was grilled in the House of Commons about his former employee. Zajdel's name was brought up during question period by eight different New Democrat and Liberal MPs.
NDP Leader Tom Mulcair pressed the government to explain why Zajdel was ever on Moore's payroll.
"If Mr. Zajdel or Mr. Applebaum have in any way broken the law they should have the book thrown at them and they should be accountable to the full extent of the law," Moore replied before listing some of the work his office has done in the city.
Zajdel had finished some 2,300 votes behind Cotler in the May 2011 election in Mount Royal — a riding coveted by the Tories as a possible beachhead in Canada's second-largest city. The riding, once represented by Pierre Elliott Trudeau, has been Liberal since 1940.
Liberal Leader Justin Trudeau called Zajdel's arrest another example of the government's "horrible judgment" when it chooses employees and senior officials.
"They are constantly mixing up the Government of Canada with the Conservative Party and such a perspective, blinded by their partisanship, leads them to very bad decisions," Trudeau told reporters.
As for Cotler, he tweeted that everyone deserves the presumption of innocence and declined to comment on the charges against his rival.
Zajdel had been a city councillor in the same Cote-des-Neiges-NDG borough as Applebaum and, in recent years, the two of them were part of the once-mighty Union Montreal political party which had won every election in the post-2001 mega-city.
Applebaum, meanwhile, will face 14 charges including fraud, conspiracy, breach of trust, and corruption in municipal affairs.
Zajdel LinkedIn profile makes no mention of his federal work for Moore's office.
It does say, however, that he spent years on the city's powerful executive committee in areas such as zoning and urban planning. The online profile said he had spent the last year as a real-estate broker and a municipal-affairs consultant with expertise in matters related to zoning, urban planning and permits.
When it comes to details about Zajdel's federal job, information has always been scarce. The Conservatives were reluctant last year to discuss his duties or his salary in the government position.
But the Tories eventually broke their silence when Moore himself came out in defence of his employee, who left Montreal municipal politics in 2009 after 23 years on council.
Moore explained that Zajdel worked in his Montreal office as a non-partisan liaison with local ethnic communities.
"Saulie was a multi-term councillor here in Montreal and he knows people and people know him," Moore said in March 2012.
"They also know that he's a hard-working, decent guy who wants to do good things for Montreal and he was unsuccessful in the campaign, but he wants to continue to serve and he's done a great job."
Zajdel's federal appointment first caught Cotler's attention after the defeated Tory candidate convened a meeting with municipal politicians in Mount Royal to explain the grants and programs offered by Canadian Heritage.
One mayor who attended the November 2011 presentation said while it was unusual to receive such an invitation from a government employee, he noted that Zajdel didn't raise partisan politics.
In his federal role, Zajdel also spoke publicly in Cotler's riding, which has a large Jewish population, about Canada's relationship with Israel.
Zajdel declined multiple interview requests to discuss his Canadian Heritage job, but he spoke candidly about his government paycheque in a chat with a Canadian Press reporter during Harper's March 2012 Montreal visit.
He revealed that he was earning less than he had hoped for.
"Oh, (it's) not as much as I want it to be," Zajdel said. When asked how much he would have liked to earn, he replied: "Something in the six digits and it's not that."
Zajdel announced a couple of weeks later that he had stepped down from his federal job. He told a Montreal radio station that he decided to quit because the controversy stirred up by the position had overshadowed Harper's announcement in the city.
"I was tired of being this distraction," Zajdel said in a radio interview with CJAD, before adding that it would be his "greatest pleasure" to run again for the Tories.
In a video posted on YouTube during the 2011 federal election campaign, Zajdel talks about himself and promotes the Tories. The images are interwoven with audio and video clips of Harper.
"I'm fond of saying to my friends and family (that) I'm just the son of an egg man who has succeeded at the municipal level and (wanted) to take it to a higher level when the call through the prime minister's emissaries came," Zajdel tells the camera while syrupy music plays in the background.
"I'm here to serve the people and that's what I've done much of my life."
But Zajdel hasn't always been a Conservative to the core. He once announced he was planning to campaign under the Liberal banner, in Mount Royal.
On Monday, the NDP distributed an old newspaper report that says Zajdel had intended to run for the Mount Royal Liberal nomination ahead of a November 1999 byelection. The article says he later decided to withdraw from the race when he heard Cotler, a prominent human-rights lawyer, was also running for the nod.
At the time, Zajdel told the Montreal Gazette that he couldn't bring himself to run against Cotler because "a man of the stature and reputation of Irwin Cotler deserves our unequivocal support."
By 2011, Zajdel had changed allegiances and decided it was time to unseat Cotler.
Shortly after Zajdel was named in March 2011 as Cotler's opponent, he told The Canadian Press that the Tories had courted him "strenuously" to run for them in Mount Royal.
The phone calls against Cotler came after the election, prompting a scolding from the House of Commons Speaker who called the tactic "reprehensible."
Zajdel did not comment on Monday's arrest. He walked briskly out of the police headquarters, bypassing news cameras, and entered an awaiting car that honked at journalists to get out of the way.
- with a file from Joan Bryden in Ottawa and Peter Rakobowchuk in MontrealSuggest a correction