There's a simple way to cull the field of candidates running for the Conservative leadership. Ask yourself: Who would Stephen Harper support?

The Conservative Party is still Mr. Harper's party. He initiated the union of the Progressive Conservative and Canadian Alliance parties back in 2003. He has been its only permanent leader. The 100,000 or so members of the party mostly joined on his watch. In the main, their values are his values. If Stephen Harper would never vote for a candidate, that candidate shouldn't be running.

While neither Mr. Harper nor his friends are offering their views, there are four criteria he would probably use. (One caveat: This is how prime minister Stephen Harper would think. How that thinking has evolved in the months since he left politics may be a different matter.)

Story continues below advertisement

Read more: Kevin O'Leary enters Conservative race, won't yet seek Parliament seat

Read more: Who's running for the Conservative leadership? Read the list of candidates

First: Is the candidate proficient in French? Mr. Harper worked hard to master the language from the time he was a teenager, and he would expect any serious candidate to make a serious effort. Neither Quebec nor Ontario voters – who would never jeopardize the peace of the realm by supporting a unilingual anglophone – would tolerate a Conservative leader who can't speak decent French.

This would appear to rule out Simcoe-Grey MP Kellie Leitch, entrepreneur Kevin O'Leary and Milton MP Lisa Raitt;

Second: Do you have support from both the Red Tory and Reform wings of the party? Reformers tend to be fiscally and socially more hawkish than their Red Tory counterparts. If you cannot unite the two wings of the party, you shouldn't lead it. This would rule out Ms. Leitch, with her Trump-Lite policies, and Mr. O'Leary, who has no roots in the party. It also undermines the campaign of Wellington-Halton Hills MP Michael Chong, whose proposed carbon tax does not sit well with Reformers;

Third: What are your organizational chops? When running for the Alliance and then Conservative leaderships, Mr. Harper set great store by his ability to out-organize and out-fundraise his opponents. Not only is it necessary to win, it tests the candidate's ability to create and lead a robust national organization. A serious candidate for the Conservative leadership should have ground games in every region of the country.

This criterion undermines the campaign of former immigration minister Chris Alexander – who otherwise would be an attractive candidate in Mr. Harper's eyes;

Story continues below advertisement

Fourth: What's your support within caucus and the party establishment? If at least a solid chunk of MPs and militants aren't with you, you will have a hard time uniting the party after the leadership vote.

Interestingly, this eliminates the candidates already named above. They fail the fourth criterion because they failed one or more of the first three.

That leaves three that Mr. Harper might prefer. Beauce MP Maxime Bernier is one of them. The former foreign affairs minister has been raising impressive amounts of money, has half a dozen MPs backing him and is popular in the West as well as Quebec. Mr. Harper fired him from cabinet and later brought him back in a more junior role, because he thought Mr. Bernier lacked seriousness of purpose. This campaign is Mr. Bernier's opportunity to refute that allegation.

Durham MP Erin O'Toole performed surprisingly well in the French-language debate, has an attractive résumé (the former veterans affairs minister was an Air Force captain who became a corporate lawyer) and is backed by 16 MPs. The biggest strike against him is that he isn't well-known outside the party.

Former House speaker Andrew Scheer has the most support in caucus: The Regina MP is backed by 24 of his colleagues and is one of the strongest contenders. However, his socially conservative disposition would not sit well with Mr. Harper, who always worried about letting the party be captured by the "God, guns and gays" crowd.

A personal guess (and that's all it is) is that Mr. Harper's ballot would look something like: 1. Erin O'Toole, 2. Andrew Scheer, 3. Maxime Bernier. This, however, could change in the months ahead.

Story continues below advertisement

Mr. Harper would sigh as he filled that ballot out; none of these candidates appears conspicuously able to challenge Prime Minister Justin Trudeau.

But then he would remember, with a grim smile, how contemptuously the critics dismissed his prospects. He knows how much election campaigns matter.