OTTAWA -- Prime Minister Stephen Harper was hoping to buff the scratches out of the Conservative campaign machine Friday after two embarrassing apologies in the space of 12 hours robbed it of its usual precision and polish.

Agriculture Minister Gerry Ritz issued his mea culpa late Wednesday after The Canadian Press reported he'd made "tasteless" jokes about the deadly listeriosis outbreak during a conference call last month.

Despite opposition calls for Ritz's ouster, Harper -- having already demonstrated zero tolerance for campaign missteps -- opted to stand by his minister, chalking the ill-timed attempt at gallows humour up to on-the-job stress and strain.

He'd barely had time to do so when word emerged about an ugly confrontation between aboriginal protesters and an aide in Transport Minister Lawrence Cannon's campaign office.

A spokeswoman for Cannon apologized after a member of Cannon's staff was caught on tape responding: "If you behave and you're sober and there's no problems and if you don't do a sit down and whatever, I don't care."

The staff member, Darlene Lannigan, then added: "One of them showed up the other day and was drinking."

The apologies conjured memories of two early Conservative missteps -- a web graphic of a puffin defecating on Liberal Leader Stephane Dion, and a campaign official's dismissive partisan depiction of the father of a dead Canadian soldier -- for which the Tories said they were sorry.

Harper was pressing on, however, steering the Tory campaign through Quebec and eastern Ontario -- the two provinces where he must shore up support if he's to claim his coveted majority government.

Dion, meanwhile, was in Manitoba and Saskatchewan, selling his Green Shift program in an energy-producing part of the country where the notion of a carbon tax is a tough sell.

The Liberal leader, who has surrounded himself with other Grit luminaries in hopes of restoring his lost leadership lustre, got a lift Thursday from none other than Jean Chretien.

The former prime minister said Harper has conveniently ignored the fact that Liberals -- not Conservatives -- did all the heavy lifting required to eliminate the federal deficit.

"We balanced the books . . . and they forget to mention that," Chretien said of Harper's persistent warnings that reckless Liberal spending would drive the country back into a deficit.

"We balanced the books, we took the heat for that and we were admired by a lot of people around the globe for that," he said on his way into a closed-door speech to a francophone business group.

"Now, some think the good old days might disappear -- but don't blame me, I'm not there anymore."

Dion campaigned Thursday in Toronto with Liberal heavyweight Michael Ignatieff, promising to spend more than $70 billion over 10 years on infrastructure improvements.

Dion said he would divert budget surpluses that exceed a $3-billion contingency fund to infrastructure projects, rather than paying off the debt as the Conservatives -- and the Liberals before them -- have done.

NDP Leader Jack Layton, who targeted the elder vote Thursday with a $1-billion home-care program for seniors, was taking time from the campaign trail to attend the Ottawa funeral of New Democrat stalwart Marion De war.

And Elizabeth May of the Greens, who has only occasionally ventured away from her Nova Scotia riding where she's taking on Defence Minister Peter MacKay, was looking for fertile ground for her campaign in Vancouver and the B.C. interior.