OTTAWA (Reuters) - A former top aide to Canadian Prime Minister Stephen Harper could reveal potentially damaging details about a corruption scandal as he takes the stand on Wednesday at a trial that threatens to eclipse the ruling Conservative's re-election bid.
Harper's former chief of staff, Nigel Wright, is the highest-profile witness to testify in the months-long trial of Conservative Senator Mike Duffy, who is accused of receiving a bribe and abusing expense claims two years ago.
The testimony of Harper's one-time confidant ramps up just as the election campaign swings into its second week, with the prime minister scheduling a trip to Canada's remote Arctic that overlaps with his appearance.
Wright resigned as Harper's chief of staff in May 2013 after it emerged he had given a C$90,000 ($68,700) check to Duffy to cover living and travel expenses the senator had claimed improperly.
Canadian police investigated Wright's involvement but dropped the probe in April.
The Duffy affair and its tales of backroom deals and undercover payments is embarrassing for Harper, who came to power in 2006 vowing to clean up Ottawa. The prime minister insists he had no idea Wright planned to give Duffy money.
The opposition New Democratic Party, running neck and neck with the Conservatives ahead of the Oct. 19 election, says Harper's trip north was strategically timed to get away from Ottawa as the trial makes headlines.
"He can run but he can't hide," NDP leader Thomas Mulcair said.
Conservative campaign spokesman Bryn Weese dismissed Mulcair's criticism, pointing out reporters were traveling with the prime minister: "We're clearly not hiding from anyone."
If Wright testifies that Harper knew about the payoff, the damage to the prime minister would be enormous.
Conservatives have said for months they do not expect the trial to implicate Harper, but concede the media coverage could make life uncomfortable.
Harper initially said Wright had resigned but as public uproar grew in 2013, he changed his tale and said he had fired him. A friend of Wright said the former aide was "not looking for revenge, he is just looking to tell the truth."
Duffy says he did nothing wrong because the rules in the Senate, Parliament's upper chamber, were so vague he was within his rights to claim the expenses in question.
Additional reporting by Randall Palmer; Editing by Josephine Mason and James Dalgleish