As if Stephen Harper needed more embarrassment in the middle of a tough election campaign, Monday will see the start of another criminal trial of a former member of his inner circle: Bruce Carson, once his senior adviser.

News from the trial may be another distraction keeping the Conservative leader from sticking to his platform points, just as questions about Senator Mike Duffy’s criminal trial knocked him off-message during the first few weeks of the campaign.

And before the Duffy trial even got rolling, Harper’s former parliamentary secretary, ex-MP Dean Del Mastro, was sentenced to a month in jail for election fraud and led away from a court in shackles on June 25. Del Mastro is appealing his conviction.

Carson will be tried in an Ottawa courthouse September 14 on one charge of influence peddling. He’s accused of using his influence as a former government official to arrange the sale of water-filtration systems to native reserves, using contacts he’d made in the Department of Aboriginal Affairs and Northern Development.

He faces possible criminal sanction for allegedly directing 20 per cent of the revenue derived from the lucrative water-filtration deals to his then-fiancée, Michele McPherson, a former escort who worked in the Ottawa sex trade.

The charge, laid in 2012 by the RCMP, says he “did directly or indirectly demand a benefit for Michele McPherson from H2O Water Professionals Incorporated and H2O Global Incorporated as consideration for cooperation, assistance, and exercise of influence for a matter of business relating to the government, namely Indian (now Aboriginal) Affairs and Northern Development Canada.”

Carson worked for Harper when he was Opposition leader as his policy and research director from September, 2004 until January, 2006. A month later, after Harper won the 2006 election, he became a senior adviser in the Prime Minister’s Office until November, 2008.

One of the questions Harper might be asked on the campaign trail is why Carson was hired to work for the PMO in the first place, given his criminal record.

In 1983, he was convicted of theft and sentenced to 18 months in prison, although he was paroled. In 1990 he was convicted of fraud; he was given probation and ordered by a court to attend psychiatric counselling.

Reached by phone, Carson’s defence lawyer, Patrick McCann, said his client “made no effort to hide the fact that he had a criminal record. It was disclosed at the time he joined the PMO and it was … you know, you need a security clearance (to work there).”

McCann, who also represents Nigel Wright, Harper’s former chief of staff — a major witness at the Duffy trial — said Carson’s hearing would be a “paper trial”, relying on transcripts of witnesses who appeared at the preliminary hearing.

McPherson testified at Carson’s preliminary hearing in June of last year, as did employees of the now-defunct water filtration company and officials from Aboriginal Affairs. None of that testimony can be reported publicly until the trial itself begins.

The influence peddling charge has not been proven. The preliminary hearing merely established there was enough evidence to warrant a criminal trial.

Perhaps Harper can be grateful that Carson’s three other charges of illegal lobbying won’t go to court until next May or June, long after the election is over.

Those charges, relating to the five-year lobbying ban imposed on political staffers after they leave government office, could — if proven — tie Carson much more directly to the PMO than the offence he’s in court for on Monday.

Carson, the RCMP alleges, was paid to lobby for the Energy Policy Institute of Canada (EPIC) and the Canada School of Energy and the Environment (CSEE). He’s accused of using his extensive contacts in government, including relationships with Wright and the then-Clerk of the Privy Council, Wayne Wouters, to steer funding towards the two groups.

An RCMP order to produce information, or ITO, filed with the court by Constable Marie-Josée Robert, shows Carson emailed Wright in 2011. He told Wright he’d never met him, but would like to get together to share a report he’d just written on energy.

“I’ve heard a lot of good things about you,” Wright replied. “Feel free to call me at any time.”

McCann said he thinks Carson’s trial Monday for influence peddling may last only a day. The Crown attorney for the case is Jason Nicol.