MOOSE JAW, Sask. - NDP Leader Jack Layton is urging voters to think strategically when they cast their ballots, so they can get rid of Stephen Harper as prime minister.

It's a risky call.

It makes sense in Saskatchewan for the NDP because the party placed second in almost every riding and didn't win a single seat because it split the anti-Harper vote with the Liberals.

But it will be a tougher argument for Layton to make Tuesday when he heads into southern Ontario and the suburbs around Toronto. There, the Liberals are often second place in Tory-held ridings, so a strategic vote would detract from the NDP.

"The way to stop Stephen Harper from getting a majority is to take Conservative seats one by one, and defeat the MPs who are there. That's how you stop Mr. Harper from getting a majority," Layton said in Regina.

"Here in Saskatchewan, just like in British Columbia, just like in Alberta where we've been to launch this early part of the campaign, the only way to do that is to vote for your New Democrat candidate."

Indeed, when Tory incumbent Andrew Scheer talks about how he is going to keep his seat in Regina Qu'Appelle, he only mentions the New Democrats when he talks about opposition.

"First and foremost a lot of (voters) are upset that there is an election. They don't think the NDP even read the budget," Scheer said in an interview. "I think Jack Layton is going to have a tough time explaining himself."

That kind of criticism doesn't bother the NDP. It vindicates their argument that they are the best way to oppose Harper.

On a stop in Moose Jaw, where the NDP has lost its traditional seat to the Conservatives, Layton framed the argument clearly for campaign workers.

"Noah (Evanchuk) will defeat a Conservative member of Parliament here," he said about the NDP candidate in Palliser.

"And that takes Stephen Harper two steps away from getting the majority that he so desperately wants to seek. Because not only do you defeat a Conservative but you elect a New Democrat. So you get a two-fer out of that."

In Alberta, the NDP is the only opposition party with a seat. The New Democrats hope to expand that by picking up a seat or two in the Edmonton area where they placed a strong second in the last election.

In British Columbia, the NDP is the main alternative to the Tories in many ridings, but not all.

But in much of the rest of the country, the strategic-voting pitch could favour the Liberals. The vote-rich area around Toronto and much of southern Ontario, for example, is mainly a tussle between the Liberals and the Tories, making the Liberals the most likely beneficiary of strategic votes.

Layton has been reluctant to criticize Liberal Leader Michael Ignatieff during the campaign so far, choosing to save his fire for the Tories. But if his strategic voting pitch is going to work east of Saskatchewan, he will have to take aim at the Liberals as well as the Tories.

NDP insiders say the key to their strategic voting pitch is "trust." Layton always scores well in polls of personality and trustworthiness, and so the campaign hopes to leverage that into a feeling of mistrust of the other two leaders.

Gun control remains a thorn in the NDP's side, however, especially in rural ridings and Northern Ontario. The Tories never pass up a chance to remind the electorate that both the Liberals and the NDP prevented the Conservatives from abolishing the gun registry. It's a polarizing issue that splits the opposition and works in favour of the Conservatives.

Layton said he's ready to confront the issue, however. He said he is proposing reforms to the gun registry so that it won't make rural gun-owners feel like criminals.