Sometimes the reasons for the return of an old story are more interesting than the story itself.

With the NDP edging ahead of the other two parties into a clearer lead, there's no shortage of people with an interest in taking the party and its leader down a few notches.

And so, as the country's political classes head home for summer, inside sources on the NDP leader's Tory flirtation make the rounds for the third time (or is it the fourth?)

The story of how Mulcair was courted by the federal Conservatives was first reported shortly after it happened in 2007, when he had just quit as environment minister in Jean Charest's Quebec Liberal government,

It came up again when the NDP needed to replace Jack Layton in 2011.

Then in 2012, the Toronto Star rehashed the story, adding a new detail that suggested Mulcair's principles might be negotiable. Mulcair insisted on a salary of $150,000, and walked away when his terms weren't met, according to that account.

In the newest version of the story, Maclean's doubles the amount Mulcair was holding out for to $300,000, an amount in the range of the prime minister's salary. Mulcair is said to have declined an offer of $180,000.

But neither story explains why Mulcair instead chose to follow a course that was both less certain and less lucrative: running for a party that held no seats in Quebec, in a riding that had long been considered a safe Liberal seat.

By winning that contest, Mulcair qualified for the salary of a member of Parliament, which was at that time about $140,000.

Mulcair says he also rejected a lucrative offer from a private law firm. "Money was never the issue, because I was still interested in serving my fellow citizens," he said.

NDP rejects claims

One of the main sources for the Maclean's story is former Conservative Party executive director and PMO director of communications Dimitri Soudas.

Soudas, who advised Stephen Harper on Quebec strategy, is no stranger to political makeovers himself, having recently aligned himself with a Liberal campaign: his partner Eve Adams, herself a former Conservative MP, is now running for a Liberal nomination in the Toronto riding of Eglinton-Lawrence.

Soudas says he made the call to Mulcair when the issue of money first came up. But Mulcair, who has always acknowledged some kind of talks with the Conservatives, denies having dealt with Soudas.

New Democrats are turning lemons into lemonade, using the story to point out that the Conservatives would not have wooed Mulcair unless they valued his talents.

"The Conservatives approached Mr. Mulcair first, via Lawrence Cannon, at the Quebec City airport," says the NDP leader's principal secretary, Karl Belanger. "In fact, it is no secret that the four federalist parties approached him once he decided to leave provincial politics. It means, of course, that they believe he is a competent, prudent public administrator."

Cannon told Maclean's that Mulcair didn't dismiss the idea of running for the Conservatives.

Belanger acknowledges Mulcair followed up on the offer.

"At the time, Mr. Mulcair thought he could serve his country as chair of the National Roundtable on the Environment and the Economy. In the end, it didn't go anywhere, because of the Conservatives' intransigent position regarding climate change.

"So Tom Mulcair made a choice based on his values, ‎based on what he believed was right for Canada. That is why he joined Jack Layton's NDP in 2007, in Quebec, a move that can hardly be described as opportunistic."

Mulcair wouldn't change his stance on the Kyoto accord to fit in with the blue team.

But as an ex-environment minister, Mulcair should have known the Conservatives' firm views on climate change. If that was a deal-breaker, why talk at all?

Embracing Jack Layton's New Democrats turned out to be an extremely good move for Mulcair. But in 2007, when the party held no seats at all in Quebec, it could hardly have seemed like a sure thing.

Who's behind the story?

Front-runners attract more attacks, and every federal party has reasons to want to poke a stick in the NDP's wheels.

But of all the parties, Conservatives perhaps have the least to gain from this particular story.

Painting Mulcair as an opportunist and a mercenary may hurt him, but it also raises the question of why the Conservatives tried to hire him as an adviser. And any future Conservative attacks on Mulcair could be blunted by the knowledge that Tories, at one point, wanted him in their ranks.

Indeed, one former senior Conservative who was intimately involved in the 2007 talks poured cold water on the idea that Mulcair was ready to throw in his lot with Harper, saying he didn't believe any amount of money would have made Mulcair a Conservative.

Soudas is now working for another party, the former PMO insider points out.

The Liberals and the Bloc Québécois are in direct competition with the NDP for the same voters, and both parties have seen their share of the electorate shrink thanks to defections to Mulcair's party.

The Bloc, in particular, has made a point of targeting the orange grip on Quebec since the return of its former leader Gilles Duceppe.

Maclean's wasn't giving away its sources, other than Soudas. It did say who they weren't: "Neither the government, the Conservative Party, nor Soudas approached Maclean's about Mulcair's negotiations."

That disclaimer still leaves a lot of likely suspects, including another political party in Quebec that would like to undermine the NDP.