This is a week when sizeable potholes have surfaced on Stephen Harper’s road to re-election.

The NDP’s majority victory in Alberta has reinforced the federal New Democrats’ claim that their party is ready for prime time nationally. At a minimum, the provincial election has exposed cracks in the walls of the country’s main Conservative fortress.

At the same time, Harper is suddenly at risk of losing the upper hand on the central battlefield of tax cuts to the Liberals.

The two developments are independent of each other, but what connects them is that they find the ruling Conservatives playing defence on two flanks that they believed to be bulletproof.

The 40 per cent of Albertans who ushered the NDP in government this week did not vote for Thomas Mulcair by proxy. And a slim majority of the province’s voters stuck with the right, either by supporting the Wildrose party or Jim Prentice’s Tories.

The good news for Harper is that those voters can be expected to unite behind his federal Conservatives next fall.

The bad news is that they are not spread evenly across the province.

On Tuesday premier-designate Rachel Notley’s New Democrats won more than 20 ridings with a majority of the vote. Many of those seats were won with 60 per cent support or more. In another half a dozen ridings, the combined score of the NDP and the Liberals added up to more than 50 per cent.

Based on those results, a sizeable contingent of Alberta voters does not come across as predisposed to support the federal Conservatives next fall.

Alberta’s 87 provincial ridings work out to 34 federal ones. The provincial results suggest that Harper’s Conservatives could be campaigning against a tide for change in more than a quarter of them, mostly in the Edmonton area.

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Conventional wisdom has it that vote-splitting between the NDP and the Liberals will still pave the way for the re-election of most of Alberta’s Conservative incumbents and that may well be right.

In the federal by-elections that have taken place in the province since Justin Trudeau became leader, the Liberals scored immensely better than Mulcair’s New Democrats. If Notley’s success translates into a bump in support for her federal cousins, the result could be a more divided anti-Harper vote, not only in Alberta, but from coast to coast to coast.

Still, in the big picture, there comes a point when two strong opposition parties, instead of eating each other’s lunches, start taking sizeable bites out of different sections of the incumbent’s pie.

That’s what happened to the Parti Québécois last year.

So far, the Conservatives have focused their attacks on Trudeau. Polls have long suggested that the Liberals, not the NDP, are the main threat to a fourth Conservative victory next fall.

But, what if, in their efforts to weaken the Liberals, the Conservatives open themselves up for a kill at the hands of a conversely strengthened NDP?

As unlikely as the scenario of a Mulcair victory may seem it is still less improbable than the advent of a majority NDP government in Alberta was thought to be only a few weeks ago.

It is a risk that Harper’s Conservatives will now need to reassess.

At the same time, Trudeau is now challenging the Conservatives on their tax-cutting turf.

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Two days after he unveiled two platform planks — a tax-cut for middle-income earners and an enhanced child benefit retargeted to middle-class families — Conservative spin-doctors are still uncharacteristically struggling to come up with an effective response.

To date, they have not managed to do better than try to bluster their way out of a trap that finds them standing up for the more affluent section of the electorate. It does not help that the trap is largely of the government’s own making.

Harper’s re-election for a fourth mandate has always hinged on a divided opposition and post-Alberta election that remains a potentially winning condition for his party.

But a week that has seen both the hands of the Liberals and the NDP reinforced at Conservative expense is not one that bodes especially well for the game plan of the prime minister.

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