Conservative Leader Stephen Harper is defending his decision to appoint Mike Duffy as a senator for Prince Edward Island, saying that the former Ottawa broadcaster met the bar of owning a residence in the province.

But simply owning a residence, and actually living in it as a "resident," are two different concepts that have been at the heart of both Duffy's ongoing criminal trial and the scandal that engulfed Harper's office.

Duffy's name came up once again on the campaign as Harper made his first visit Thursday to the island to announce $20 million in trade marketing and research for the lobster industry.

Four years ago, Duffy would have been at such a campaign stop. He would sometimes act as the energetic master of ceremonies at the leader's rallies.

Now questions about Duffy and the PMO's efforts to make the issue of his expenses go away continue to follow Harper.

"From the day that Mike Duffy was appointed a senator for Prince Edward Island, everyone in this room could tell you he was not a resident in P.E.I.," asked a reporter with the Charlottetown Guardian.

"I'm just wondering if you could explain, why did you appoint Mike Duffy to represent Prince Edward Island?"

"We only appoint a person to the Senate when they have a residence — not just property, but a residence — in the province in which they are representing, and that fit that case as it fits every single case of a senator that we have named," Harper said.

Internal PMO emails entered as evidence at Duffy's fraud, breach of trust and bribery trial show that Harper took a hard stand on the constitutional requirements to sit in the Senate.

Defining 'resident'

The Senate refers to two criteria for eligibility: that an individual own at least $4,000 worth of real property in a province, and that the person be "resident" in the province.

For Harper, owning the $4,000 in property meant that a person was "resident." He rejected PMO lawyer Benjamin Perrin's suggestion that certain indicators be developed to better define what being "resident" meant, and defended Duffy's qualifications in the House of Commons.

Duffy had worked for decades in Ottawa as a broadcaster, and at the time of his appointment lived in the suburb of Kanata, Ont., and owned a non-winterized cottage in P.E.I.

Crown attorney Mark Holmes said at the outset of Duffy's trial that he did not consider the senator to be constitutionally eligible to represent the province.

That issue is not part of the trial, but rather whether he defrauded the taxpayer by operating as though he lived in P.E.I. while filing expense claims for his home in the Ottawa area.

Responsibilities of office

Harper emphasized he did not approve of Duffy's actions around expenses.

"Anybody who's been appointed to the upper chamber by me and frankly by previous governments are all people who have had considerable success in life, and they respect the responsibilities of office," he said.

"I think all Canadians have a right to expect at all times the highest standards of behaviour from them."

The Conservatives have challenges ahead of them in Atlantic Canada, where there are areas of nagging unemployment and underemployment.

Harper announced that if re-elected he would invest in a $15-million partnership with the Lobster Council of Canada to market and promote lobster abroad, plus $5 million in research with local universities and institutes, over three years.