Political costs could be high for party leaders.

MONTREAL— In the matter of the just-concluded Trans-Pacific Partnership (TPP) agreement, the political benefits and the potential costs are divided unevenly among the parties competing for government in the upcoming election.

Conservative Leader Stephen Harper took a risk by pursuing a major trade agreement in the midst of a campaign. He could not, under any scenario, guarantee its ratification by Parliament. But on the election trail, he is ultimately the least exposed by the outcome of the negotiations.

A commitment to freer trade is one of the stronger ties that bind the fractious factions of his Conservative coalition.

It is a rare signature policy of the former Progressive Conservative party that Harper has whole-heartedly made his own. Tories of all persuasions will be happy selling the TPP.

Support for this agreement extends well beyond the ranks of the Conservative party. One of the perks of government is the capacity to reach out to economic stakeholders. Harper has had weeks to line up positive reviews of a deal. Even before he appeared at a news conference to champion the TPP on Monday, fans of the agreement had lined up to laud its virtues.

Meanwhile, its most likely critics — starting with Canada’s dairy industry — have been, if not silent, at least appeased by the prospect of rich compensation packages.

The Harper cabinet has pre-approved more than $4 billion in payouts to the dairy farmers who might lose income over the opening up of a fraction of the Canadian market to the other TPP countries.

Canada’s supply management system has been in the sights of the country’s trade partners for more than a decade.

Only in their dreams could its proponents hope for a softer landing. As the Dairy Farmers of Canada tweeted shortly after the announcement: “No negative impact and supply management preserved for a generation.”

Politicians are never as generous as when they are campaigning for re-election and the dairy industry can probably thank its lucky stars that crunch time at the TPP table coincided with the 2015 campaign.

Compared to Harper, NDP Leader Thomas Mulcair — who has declared the TPP a bad deal for Canada — sits at the high end of the risk spectrum.

The powerful movement that opposed the initial free-trade agreement and North American FreeTrade Agreement at the time of the 1988 and 1993 elections is, by now, a shadow of its former self.

Moreover, by talking up arms against the TPP, Mulcair is throwing out years of efforts to sell the NDP as a party that has made its peace with globalization and freer trade.

His anti-TTP stance pits him not only against corporate Canada in general but against its influential Quebec section in particular. On Monday, the Montreal Chamber of Commerce, aerospace giant Bombardier as well as a host of Quebec meat and fruit producers associations, all came out in favour of the agreement.

The Bloc Québécois, for one, took notice of the way the wind seemed to be blowing.

As recently as Friday on the stage of the second French-language leaders debate, Gilles Duceppe was accusing Harper of being about to sacrifice Quebec’s dairy industry on the TPP altar.

But with the highlights of the actual deal in hand on Monday, Duceppe softened his tone.

The Bloc is disappointed by the agreement but not disappointed enough to rule out supporting its ratification in the House of Commons.

Opposing the TPP might help Mulcair hang on to the union votes in the auto-industry heartland of southern Ontario but it does go against Quebec’s pro-free-trade bias.

The NDP position stands to be seen by many voters as a purely defensive move dictated by the party’s loss of its front-runner status in voting intentions and its need to try to shore up its base in the face of erosion to the Liberals.

And what of Justin Trudeau? For now he is keeping his options open — promising to not ratify the agreement before it has been fully aired in the next Parliament. But the days when a Liberal leader promised to tear up free trade deals are long behind the party.

Trudeau can only hope that Mulcair won’t be as effective fighting the TPP between now and Oct. 19 as he was opposing the Conservative anti-terrorism legislation last spring.