In the Provencher by-election in November the Conservatives went from 27,820 votes (70.6% of the vote) to 13,046 (58.2% of the vote), still more than enough to win but a loss of more than half the Conservative supporters The non Conservative vote went from 11,075 to 9,371, only a drop of about 15%. No one was paying attention to this race still it was much closer than expected.
In 2012 in Calgary Centre was saw a similar dramatic fall in Conservative support but a much steadier support for the other three parties.
The margin of victory for the Conservatives in Macleod is even higher than Provencher or Calgary Centre which means the chances of losing are significantly lower making it more less impossible for the Conservatives to lose. Everything in Macleod will come down to voter turnout in the by-election. A low turnout will benefit a non Conservative that is running hard but even then the chances are very astonishingly small that the Conservatives could lose.
For the last several years I have been doing in depth analysis of federal by-election turnouts to see what patterns I can find among them, one of the biggest is that in safe seats the incumbent party supporters stay home. When I look at the last 64 by-elections, my estimate for the voter turnout in Macleod would be for 27,500.
Based on past election results for the non Conservatives, in the by-election they likely to achieve about 9,000 to 10,000 votes, which leaves the Conservative candidate with about 18,000 votes. This would be a landslide win for the Conservatives.
The gap between the nadir of the Conservative support and the combined non Conservative vote is huge and I do not think there is any chance the Conservatives could lose this.
If in the by-election the turnout was worse than average for this sort of riding it could go as low as a 22,000. If the non Conservatives could retain 90% of their 2011 vote, this would still leave the Conservatives with 12,000 votes and a large win.
For the Conservatives to lose this seat something dramatically different would have to happen - a whole bunch of red necks would suddenly have to embrace Justin Trudeau, something that the Manitoba by-elections indicated did not happen.