Michael Ignatieff and Jack Layton could very well end up working together after May 2, but until then, the NDP Leader is going all out to portray his Liberal counterpart as an untrustworthy politician who doesn't show up for work.
Starting with the debates, when Mr. Layton surprised Mr. Ignatieff by challenging his attendance record for parliamentary votes, the NDP has been on the attack in TV ads and on the campaign trail.
The approach appears to be helping the NDP, which is trending upward in some public-opinion surveys. Mr. Layton's personal approval is also rising - according to Nanos Research - while Mr. Ignatieff's personal numbers slide.
For the Liberals, results from some polling firms suggest they should be encouraged by regional races with the Conservatives that are tightening. Other poll numbers suggest a risk of being overtaken by a gaining NDP.
Yet Liberals won't return the NDP fire. The party is of the view that there are many votes to be gained by tapping into the majority of Canadians who oppose Stephen Harper. That means a continuing focus on the Conservative Leader - combined with warnings about health care - is viewed as a more effective way of wooing NDP voters than a direct counterattack on Mr. Layton.
The kid-gloves approach to the NDP could be seen in Mr. Ignatieff's comments Monday.
"If I make an appeal to voters with other parties, I say don't just vote negatively," Mr. Ignatieff said during a campaign stop at a mining training centre outside of Yellowknife.
He listed health care, child care, the environment and foreign affairs as areas where Liberal policy may appeal to supporters of other parties.
"If they want them, vote Liberal," he said. "Because if you don't, you get four more years of this and boy, do you know what that looks like."
In spite of his anti-Liberal attack ads, Mr. Layton indicated Monday in an interview with CBC's Peter Mansbridge that he's prepared to work out a governing plan with other parties should the first-place party in the May 2 election fail to win the support of the House of Commons.
"We come up with a common agenda," explained Mr. Layton, declining to name specific parties in this hypothetical arrangement. "There are some compromises that need to be made - well, of course there would be - but let's see how much we can get done together; it could be informal, it could be case by case."
A stronger showing for the NDP could mean an easier path to power for Conservative candidates in some ridings as the centre-left vote splits between the Liberals, NDP and Greens. In Quebec, more support for the NDP could win additional seats for the party, but it could also help the Bloc Québécois in ridings where the federalist vote splits three ways.
Conservatives know all too well the power of vote-splitting: The Liberals managed to win three back-to-back majorities from 1993 to 2000 thanks in large part to a politically divided right.
But when asked, Mr. Ignatieff rejected the idea that Canada's left will also have to merge.
"I don't think of the Liberal Party of Canada as a party of the left. I never have," he said, noting the Liberals have a history of working with the NDP on issues like health care under the Pearson government.
"We've always had good alliances, because there's common ground here, but we're not a party of the left. We're a party of the progressive centre," Mr. Ignatieff said.
With a report from Gloria Galloway in Ottawa