David Johnston's position is barely tenable. Can his investigation be salvaged?

As always, multiple things can be true at the same time.

David Johnston can be both a flawed choice to investigate the government's response to intelligence on foreign interference — and the target of unfair treatment since taking on that task. The prime minister could have been better off asking someone else to be special rapporteur — and Johnston's reception from his critics may have diminished the number of people willing and able to do the job.

Now that most members of the House of Commons have called on Johnston to resign, his position is barely tenable. But he is apparently determined to finish the job. And the process he initiated may still be salvageable.

In Johnston's telling, the extent of his relationship with Trudeau — what Johnston himself has referred to as their "so-called friendship" — has been overstated. According to Johnston, he knew Pierre Trudeau and the former prime minister's sons went skiing with Johnston's family when Johnston had a condominium near Mont Tremblant in Quebec [Johnston says the elder Trudeau had a home 50 km away]. On one occasion, Johnston said, he drove the Trudeau boys to their mother's house, 10 km away from Johnston's condo.

According to Johnston, he and Justin Trudeau occasionally crossed paths when Johnston was the principal of McGill University and Trudeau was a student there (Trudeau graduated in 1994). They had no further interactions, he said, until Trudeau was an MP (he was elected in 2008) and Johnston was appointed governor general (Johnston assumed that office in 2010).

Johnston was still governor general when Trudeau became prime minister. The Trudeau family lives at Rideau Cottage, which is located on the grounds of Rideau Hall, the governor general's residence.

Based on those facts, it's at least a stretch to describe Johnston as Trudeau's "ski buddy," "neighbour" or "personal friend," as the Conservative Party has taken to labelling him.

WATCH: Pierre Poilievre questions David Johnston's decision not to recommend a public inquiry

But given those facts — and the fact that Johnston was involved with the Trudeau Foundation after his time as governor general came to an end — Trudeau surely would have been better off finding someone else to act as the prime minister's special rapporteur on foreign interference. At the very least, Trudeau and his advisers should have anticipated the attacks Johnston faces now.

Johnston's desire to say yes whenever a prime minister asks for help is admirable. But in this case, it seems like the prime minister asked him to jump into a tank of piranhas.

There is surely much to be said for Johnston. And if it was a mistake for Trudeau to tap him for this job, presumably it was also a mistake for Stephen Harper to ask Johnston to advise him on an inquiry into Brian Mulroney's dealings with Karlheinz Schreiber (the Mulroney government appointed Johnston as chair of the National Roundtable on the Environment and the Economy in 1988) and to extend Johnston's term as governor general in 2015 (putting Johnston in a position where he had to preside over an election that prominently featured Trudeau).

But if Trudeau needed to find someone whose background was beyond question. Johnston was not that someone.

Mind you, the past few weeks might also lead one to wonder how many perfectly unimpeachable people there are in Canada.

While the headline item in the NDP's motion this week was the call for Johnston to resign, the most interesting part of that motion was an instruction to a House of Commons committee to recommend an individual who could lead a public inquiry into foreign interference. The motion says the individual should have the "unanimous support" of all recognized parties.