Tom Flanagan believes that Harper is still smarting from the last time he reached out to help the Quebec premier.
In a controversial decision, during the dying days of Quebec's tight election campaign in 2007, Harper ramped up federal transfers that netted the province $2.3 billion.
Charest quickly turned the cash into $700 million of income-tax cuts, helping him pump enough life into his wilting campaign to squeak out a new, minority mandate.
The move surprised Ottawa, as it undercut the longstanding argument for larger transfers: namely, that the provinces couldn't afford services without extra cash. Meanwhile, other angry premiers felt short-changed and unloaded on Harper, accusing him of buying votes in Quebec.
What did Harper earn in return for helping Charest's Liberals in 2007? A "kick in the teeth," according to Flanagan.
Despite Harper's headaches, Flanagan says Charest did nothing to repay the favour. Instead, he points to how the premier has repeatedly attacked federal Conservative policies on issues such as crime and the environment.
The most frustrating example, Flanagan suggests, came when Charest intervened during the 2008 federal election to criticize Ottawa's cuts to culture programs. While the amount at stake was relatively minor, at $45 million in cutbacks, the move was unpopular in Quebec and Charest joined the list of Tory critics.
Harper's Tories swiftly lost ground in Quebec and now hold just five seats in a province where Harper remains deeply unpopular.
Flanagan doesn't think Harper would buy the argument that Charest had to be critical during the federal campaign as a way to maintain his credibility with Quebec's soft nationalists.
"There's a time and place for that kind of thing — and coming out in the middle of the 2008 campaign was not the time," Flanagan said in an interview.
"Sabotaging somebody else's campaign is not an expression of good faith. That would be an injury that I would never forget if I were a political leader.
"I would be looking for revenge for that one."
Charest might not even be the prime minister's preferred choice in this election, Flanagan says. For that distinction, he could face competition from Coalition Leader Francois Legault.
As for the Parti Quebecois, which is considered the front-runner, Flanagan suggests there is even a potential silver lining if the pro-independence party wins.
The PQ is pushing for a transfer of powers and in some cases, such as Employment Insurance, Flanagan says the party's demands would be worth discussing because they might actually make the country work better.
"Well, my God, if they want it by all means let's unload it — it's been a money-loser for Canada, forever," he said about EI, noting that a constitutional amendment would be necessary to make it happen.
"Something like that I think is worth talking about... So, I don't know that you should let opposition to separatism blind you to the merits of what a PQ government will ask for."
Dogged by widespread corruption allegations after nine years in power, Charest is facing tough competition from the PQ and a rising new party, Legault's Coalition. The premier is now considered a longshot to win re-election on Sept. 4.
Flanagan, who served as Harper's chief of staff until 2004, expects the prime minister to let nature run its course this time around.
The Tories might even prefer to work with Legault, he added.
The slightly more right-of-centre CAQ is led by Legault — a former PQ cabinet minister, airline executive and accountant — who has promised to put Quebec independence on the back burner. Legault wants Quebec to focus instead on building its economy.
The CAQ absorbed the right-wing Action democratique du Quebec, a party that shared supporters and had a program Flanagan says was consistent with the federal Tories.
He believes the CAQ and the ADQ "talk the same language, to a degree" and have a similar voter base — much of it concentrated in the Quebec City region.
"It's hard to know what Legault really stands for, he's been all over the map and he was a separatist, of course," said Flanagan, a political scientist at the University of Calgary.
"But he's been talking language of economic rationality, which would certainly appeal to Harper... So, that would be to my mind actually fairly promising if Legault should happen to win."
He believes Legault could even be Harper's first choice as the next Quebec premier.
Still, Flanagan recalled how, in private, he heard Harper compliment Charest, a former leader of the federal Progressive Conservatives.
One of those times, Flanagan said, came after the 1997 election when Charest led the PCs to 20 seats, rebounding from the vote four years earlier that had reduced the once-mighty party to just two ridings.
"I think that Harper respected his political performance and certainly was willing to try and establish a relationship with him, once they both were heads of government," he said.
"But as I say, it didn't really turn out that well."
A former Quebec Tory MP, who is running against Charest's Liberals in the provincial election, recalled how the premier lost lots of credibility among Conservatives when he turned that 2007 "gift" into tax cuts.
Luc Harvey, who recently relaunched the long-dormant Conservative Party of Quebec, said Charest's move put Quebec Tory MPs in a tough spot.
He said they had the difficult task of explaining the premier's decision to use the cash for tax cuts after Charest had told Ottawa he needed the funds for things like health care.
"Mr. Charest did not keep his word on where this money would be spent," said Harvey, whose small party is not affiliated with the federal Tories.
"It was a good short-term strategy, but not necessarily for the long term."
Asked if Charest can expect more help from Harper in this campaign, Harvey replied: "Never."
"I think that everyone would say, 'We're just going to let him sink,' " said the Quebec Tory leader, who lost his federal seat in 2008.
A former Conservative staffer from Quebec also said the governing party has changed since 2007, when it had a larger Quebec caucus and was counting on big gains in the province in its strategy to win a majority government.
He said the chances of federal help for Charest, this time around, are close to nil.
"It would really surprise me," said the ex-Tory staffer, who asked to remain anonymous.
"The makeup of the federal Conservative caucus has changed. At the time, who was the Quebec lieutenant? It was Lawrence Cannon, who was a bigshot in the provincial Liberals.
"So to avoid a PQ win, they may have given money to Quebec without knowing where that money was going. I don't think anyone was expecting that (tax cut)."
The Prime Minister's Office declined to comment on the subject, but a spokesman downplayed how plugged in Flanagan still is.
"He hasn't been around for years, basically since forming government," Andrew MacDougall wrote of Flanagan in an email.
-with a file from Jonathan Montpetit
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