OTTAWA - A routine spending vote Friday will uncork and drain the latest toxic sitting of Canada's long-running minority Parliament for the three-month summer recess.

But in the words of one well-connected political scientist, that will still leave two scorpions in a bottle.

No matter how you parse this week's election-averting "collaboration" between Prime Minister Stephen Harper and Liberal Leader Michael Ignatieff, the two political adversaries will return in September to renew their confidence showdown.

"It's like two scorpions in a bottle," Tom Flanagan, Harper's former chief of staff and campaign strategist, said in an interview Thursday.

"They can't get out and they're stuck with each other."

The spring session of Parliament ended much as it began in late January, with a crescendo of empty Opposition threats that resulted in strategic government backpedaling -- with a timetable set for a repeat performance in a few months' time.

Harper's Conservatives ended more than a decade of surplus federal budgets with a massive spending document on Jan. 27. It earned only grudging "probationary" support from Ignatieff's Liberals, and none at all from the Bloc Quebecois and NDP.

The session ends with the Tories promising changes to the Employment Insurance system, designed in co-operation with Liberals, in return for another Grit extension to late September.

Harper says it would be "crazy" to suggest this week's deal simply postpones the fall of his government until the autumn.

"We could be defeated every other week on something in September, October, November, December," Harper said after concluding a deal to get Liberal support for Friday's session-ending vote on the supplementary spending estimates.

"That's the nature of a minority parliament. But I don't think the public wants surprises and I don't think the public wants an unnecessary election."

It's a far cry from Harper's declaration of political war last November, when the freshly re-elected prime minister cemented his reputation for ruthlessness by attempting to financially cripple his opponents under the guise of an economic update.

Flanagan, Harper's former mentor who has returned to academic life at the University of Calgary and become one of the Tory government's most insightful critics, argues the prime minister is still digging out from that blunder.

He said Harper should spend the summer showing his too-seldom-seen powers of negotiation, "sort of rehabilitating Mr. Harper's image, stressing the co-operative side."

A more conciliatory Harper, coupled with competent management and any slight signs of the recession easing, said Flanagan, will go a long way to staving off the government's defeat.

"I think it would be in Mr. Harper's interest -- just his crass political interest -- by buying him more time in office. But at the same time it would give the Liberals some influence."

That's not to say ubiquitous Tory ads targeting Ignatieff, powered by the bulging party war chest, will suddenly vanish from the airwaves.

"If the Conservatives have that financial advantage, they'll use it," Flanagan shrugged. "If the Liberals raise the money, they'll be doing it too."

The Liberals find themselves with a three-month breathing space before their next self-imposed confidence deadline.

Eddie Goldenberg, a top adviser to former prime minister Jean Chretien, said all opposition parties must operate on multiple tracks -- holding the government to account by publicizing shortcomings, preparing policy for the next election, and organizing on the ground.

"Most of that is done without much publicity," he said Thursday. "You do it quietly and it's a good thing to do over the summer."

Because a minority government can fall at any time, the Liberals have to pull their act together quickly.

"They don't have the luxury of time," said Goldenberg.

That's where the two scorpions in the bottle intersect.

Ignatieff was unable this month to present the public with a compelling narrative -- a ballot question -- about why an election was needed. It's his summer project to craft that narrative.

Harper's job, says Flanagan, is to make the current entente work.

"Right now, it's a Harper-Ignatieff condominium -- whether anybody wants to admit it or not," he said.

"We may as well approach it a little more co-operatively and try to get some things done."