Mike McDonald was 2013 campaign director and former chief of staff to B.C. Premier Christy Clark. He is now a senior associate with Kirk & Co. and Pollara Strategic Insights

As Ontario PC members and interested observers brace for the finale of an unanticipated and compressed leadership race, they may wish to take note of how BC Liberals recently selected Christy Clark's successor using basically the same voting system. Instead of outrageous politics, the boring math will decide the next PC leader, and maybe the next Ontario Premier.

Three key points:

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1) Some votes count more than others: In British Columbia, Andrew Wilkinson prevailed in the six-candidate race despite having the fifth-highest number of votes on the first count. How did he win?

It's a weighted ballot. Every riding is created equally. A riding is worth 100 points, and points are allocated according to the percentage of votes received by each candidate. In Mr. Wilkinson's case, while he had the fifth-highest number of raw votes on the first count, he had the third-highest number of points because he did well in ridings that had low membership levels (mainly in B.C.'s Interior) where his supporters had higher impact.

Another candidate, Michael Lee, had more votes than anyone in the race but finished third because his support was concentrated in ridings with big membership lists.

2) First choices are important, but second and third choices will decide: It's a preferential ballot, meaning that you only vote once and you have the opportunity to rank your choices. In the Ontario PC race, there are four candidates.

Mr. Wilkinson started third on the first ballot with only 18 per cent of the weighted votes, but he won. He made huge progress on the third count, and by the fourth count he was second, ultimately winning on the fifth and final count. He climbed throughout the counting process because he accumulated more second and third choices than any other candidate. He especially gained from former finance minister Michael de Jong, with whom he had a formal alliance to support each other as second choice, and from Mr. Lee, whose supporters decisively preferred Mr. Wilkinson over his final-ballot rival, Dianne Watts.

3) Not every voting member stays in the "convention hall" to the end: In the old days, delegates voted on the first ballot, heard the result, then lined up and voted again, and kept doing so until one candidate had a majority. In the Ontario PC system (as was the case in B.C.), members do all of their voting in advance, which means ranking their candidates from 1 to 4. However, they do not have to rank all of the candidates. They can just vote for their first choice if they want, but they might find that their ballot won't count when it comes down to the final two candidates.

In the BC Liberal race, about one-quarter of the voters who cast a vote on the first count did not have their ballots considered on the final count. They had essentially "walked out of the convention hall" as they did not express a preference for either Mr. Wilkinson or the runner-up, Ms. Watts. Since they had only voted for candidates already eliminated, their ballots were removed from the counting process. Smart candidates will plead for second and third choices from voters who might otherwise "leave the hall."

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The outcome in B.C. was certainly unpredictable. When it comes down to who wins, the next Leader of the Ontario PCs may be the one who is the best at math.