A record of forecasts vs. results can be found below - the barometer has only made the wrong call once in 36 federal and provincial by-elections since 2012, for an accuracy rating of 97.2%.
Note that the one error, in the Newfoundland and Labrador riding of Virginia Waters, was won by a handful of votes by the Liberals, who were given a 33% chance of taking the riding by the model. The PCs were awarded a 61% chance of winning, two points above the bar for being considered a 'Toss-Up'.
What the By-Election Barometer is
The By-Election Barometer tracks all scheduled and upcoming federal and provincial by-elections. The percentages shown in the charts represent margins, colour-coded according to the standards adopted by this site. The first set show the results of the last two elections.
The second set of margins are those that the projection model churns out when each regional/provincial poll is applied, using the same system as ThreeHundredEight's standard seat projection model. These are a way to demonstrate what might be expected in the riding, based on regional trends. The rolling 30-day average calculates an unweighted average of these projections with the last 30-days of regional polling.
The third set of margins, when available, represent the results of actual polls of the riding that have been released.
Finally, ThreeHundredEight's Forecast is calculated by taking the projected range of results from the average of the last 30 days of polling, including any polls done for the riding itself, and comparing how the ranges for each party overlap. The amount of overlap that potentially puts a party in a position to win is then tallied, the result being a percentage "chance" of that party winning the riding.
A Strong result means a 95% to 100% chance of winning, Likely is a 75% to 94% chance, Lean is a 60% to 74% chance, and Toss-Up means the chances of a party winning are 59% or less.
The Wildcard section describes any factor that could make the result unpredictable.
What it isn't
The By-Election Barometer is not a poll, the section titled "Margin after application of swing from regional polls" is not a list of riding polls, and the 30-day average is not a projection. By-Elections are notoriously hard to call, and the Barometer is not a tracking of actual voting intentions. The forecast is also not an opinion. As always, I am tied to what the numbers show.
By-elections are scheduled for October 27 in the provincial ridings of Calgary-Elbow, Edmonton-Whitemud, Calgary West, and Calgary-Foothills in Alberta, for November 5 in the provincial riding of Conception Bay South in Newfoundland and Labrador, and for November 17 in the federal ridings of Whitby-Oshawa in Ontario and Yellowhead in Alberta and the provincial riding of Saint John East in New Brunswick. By-elections have yet to be called in the provincial ridings of Trinity-Bay de Verde and Humber East in Newfoundland and Labrador, Lloydminster in Saskatchewan, and Richelieu in Quebec.
Due to the Saint John East by-election taking place so soon after the last election, and no polls are likely to be available, a forecast will not be made for it.
Like most ridings in Alberta, Calgary-Elbow has been primarily represented by Progressive Conservatives over the last four decades, when it was created. It was the riding of Ralph Klein for almost two decades. Only once, after a by-election in 2007 to replace the former premier, did any other party hold the riding. The Liberals then narrowly lost it in the subsequent 2008 provincial election. Redford won it by just under three percentage points that year, but won much more comfortably in 2012 when the Liberal vote collapsed and Wildrose surged from 7% to 29% in Calgary-Elbow.
But the outrage at Redford's antics makes this riding a difficult one to call. Will her Tory replacement, Gordon Dirks, be punished in her place? Will Wildrose be able to capitalize and steal the riding away? Or will the Liberals, who have been showing some decent life in Calgary of late, benefit from a PC slip and corral the anti-Wildrose vote? It is a riding that could go any which way, and potentially three parties could be in the running.
For now, however, the fundamentals of the riding and current polling levels point to a probable PC hold.
Forecast history: LIKELY PC since Redford's resignation, became STRONG PC on October 17.
But it may not change hands. Edmonton-Whitemud did opt for the Liberals in 1988 and 1993, but it has otherwise been a safe PC riding. And it has been becoming safer. Hancock, who held it since 1997, won it with 46% of the vote in 2004, 58% in 2008, and 60% in 2012.
Even with the PCs' drop in support, Edmonton-Whitemud should still be expected to be retained, particularly with former mayor Stephen Mandel as the PC candidate. Wildrose took just 16% of the vote here in 2012, with the Liberals at 12% and the NDP at 9%. Unless one of these parties can corral the anti-PC vote, the Tories should be able to hold it without issue.
Forecast history: Was STRONG PC from Hancock's resignation.
The riding has been held by the Progressive Conservatives for 43 of the last 47 years, with the Liberals briefly halting the Tory streak in 1993.
Hughes won the riding in 2012 in his first political run with 50% of the vote, hardly different from the 48% the party took in 2008 or the 52% in 2004. It makes the riding a rather stable one for the Tories.
But not for the other parties. The Liberals finished second with 32% in 2008, but fell to just 7% in 2012. Instead, Wildrose surged forward to place second with 37% of the vote. That makes Calgary West the riding won by the smallest margin of those heading for a vote on October 27.
Though Wildrose has about as much support in the polls now as they did on election night in 2012, the PCs have dropped considerably. That puts Wildrose in a better position to take the riding, and the forecast narrowly favours the party. But will Liberals move back to the PCs to keep out Wildrose like they did in 2012, or will Wildrose manage to wrestle this riding away?
Forecast history: Was LEAN WILDROSE from Hughes' resignation.
Prentice is not a shoo-in. But the riding has been safely PC since time immemorial. Webber won it in 2012 with 54% of the vote, an increase on his performance in 2008. Wildrose placed second with 34%, with the Liberals and NDP in single digits.
Certainly, Prentice has to be favoured since he is the premier. But without his name on the ballot, the forecast would have considered Wildrose to be the slim favourite due to the PCs' drop in support in the polls. Prentice probably has the star-power to hold the riding for the Tories, but if a message can be sent to the PCs somewhere it is certainly in Calgary-Foothills.
Forecast history: Was TOSS-UP (PC/WILDROSE) from Webber's resignation. Became LEAN PC on October 17.
The riding has been a Flaherty riding for some time. Though he only first represented the riding after the 2006 election, when he won 44% of the vote in a relatively close contest with the Liberal incumbent, he represented the provincial riding of Whitby-Ajax for the Tories before that. When he made the jump to federal politics, his wife Christine Elliott filled in and has held the riding since.
Flaherty's margins of victory were much larger in 2008 (51% to 26% for the Liberal candidate) and 2011 (58% to 22% for the NDP candidate), so it seems unlikely that the riding is seriously at play. The only wildcard in the race may be the series of strong by-election results the Liberals have put up under Justin Trudeau.
Forecast history: Was a STRONG CONSERVATIVE at Flaherty's death.
This is a very safe seat for the Conservatives. The party has taken over 70% of the vote in each of the last three federal elections. It has only been held by a conservative of one stripe or another since its creation in 1979.
Even if the Conservatives have dropped a little in Alberta, it is a riding that should easily stay in their hands. But the same would have been said about ridings like Fort McMurray-Athabasca or Brandon-Souris, so we cannot count out the possibility that the Liberals could manage another surprising performance.
But Yellowhead may not be a particularly good riding for them. The party took just 4% of the vote in 2008 and 3% in 2011. The Liberals have never had more than 22% support in the riding.
The New Democrats may have a better chance of finishing second, as they have done in the last three elections. But they were distant seconds, with between 11% and 13% of the vote. This is a Tory lock.
Forecast history: Was STRONG CONSERVATIVE from Merrifield's resignation.
The riding has been a very safe PC seat for quite a long time, having been held by French since 2002 and his father before that since 1996. The Liberals do have some history here, however, having held the riding between 1989 and 1996 as well as in the 1970s.
But lately it has been a PC landslide. The younger French won it in the by-election to replace his father with 82% support. That increased to 83% in 2003, fell slightly to 79% in 2007, and dropped further to 69% in 2011. But despite the 10-point drop, he still won it by 45 points.
His main opponent has traditionally been the Liberals, and it will likely be again based on the latest polls. But the party only took between 11% and 16% in the three elections prior to 2011, when its vote dropped to just 7%. It was instead the NDP that surged forward, from 4% in 2007 to 24% in 2011. However, the fortunes of the NDP have sunk dramatically since then.
So it should be another PC-Liberal battle. Do the Tories have enough of a head-start to hold off the Liberals here? They have been unable to withstand them in recent by-elections, even in normally comfortable ridings. Conception Bay South is an especially comfortable riding for the Tories, but I wouldn't count the Liberals out.
Nevertheless, because of the history of the riding is it currently projected as a STRONG PC and that is unlikely to change.
Forecast history: Was STRONG PC from when French announced his upcoming resignation.
This riding has tended to go with the governing party, being held by the PCs from 2003, the Liberals from 1989, and the PCs before that. It may be ahead of the curve if it goes with a Liberal MHA in this by-election, as it is expected to.
Trinity-Bay de Verde has been won by comfortable PC margins since 2003, with Johnson taking 63% in that election, 72% in 2007, and 62% in 2011. Over that time, the Liberals have taken between 23% and 32% of the vote. Considering the gains the party is making in the polls, that is enough of a base to wrest the riding away from the government, as we have seen elsewhere.
But perhaps the PCs will get a new lease on life under new leader Paul Davis. The by-election here will be a test.
Forecast history: Was STRONG LIBERAL from Johnson's resignation.
Humber East has been one of the safest ridings for the Tories under Marshall. He first won it with 60% of the vote in 2003, but increased that to 84% in 2007. His share fell slightly to 78% in 2011, but that was still a huge margin.
The Liberals, who held the riding from 1996 to 2003, were previously the main opponents. The party took 40% in 2003. But that plummeted to 11% in 2007 and then just 8% in 2011. The NDP moved into second with 13% in that election.
But the New Democrats have taken a big step backwards, and the Liberals are likely to move back into second. They don't have a large enough base, though, to be in a strong position to win it. Nevertheless, the Liberals' by-election streak of late has been impressive and cannot be discounted.
Forecast history: Was STRONG PC from Marshall's resignation.
The riding is a safe one for the governing Saskatchewan Party, which has held it since 1999. McMillan first won it in 2007 with 61% of the vote, and he increased his share to 66% in 2011. The New Democrats captured just 29% of the vote in that election, making Lloydminster almost representative of the province's wider opinion.
That being the case, Lloydminster is a lock for the popular Saskatchewan Party. It will be interesting, though, to see if the NDP can make some gains or if the Liberals or Greens can make a splash in a low-stakes by-election.
Forecast history: Was STRONG SASK. PARTY from McMillan's resignation.
The Pas is a very solid and very safe NDP riding in Manitoba. It has been held by the party since 1969, and since 2003 has been won with at least 65% of the vote. Whitehead captured it with 73% in 2011, little different from the 75% he took in a 2009 by-election.
The Progressive Conservatives took just 23% of the vote in 2011, with the Liberals at an infinitesimal 3%.
Despite the NDP's sharp drop in the polls, that margin is still too wide for the Tories to overcome. By-elections can be strange beasts, of course, and perhaps the Tories' momentum combined with a strong showing by the Liberals, who have put up good numbers in recent by-elections, could make it close. But the riding is considered a STRONG NEW DEMOCRAT.
Forecast history: Was STRONG NEW DEMOCRAT from Whitehead's resignation.
Though Zakaïb's vote share dropped between 2012 and 2014, from 43% to 39%, her margin actually increased by a little more than a point and 600 votes. And Richelieu has been safely in the PQ camp since 1994.
But the PQ's vote has been tanking, and it leaves the riding vulnerable to a flip. The CAQ is doing better in the polls, and though its support fell from 32% to 27% here over the last two elections, it remains in the best position to capture the riding from the PQ. The Liberals, who took 26% of the vote, could also make some noise in a close three-way race, but the polls do not suggest the party is poised to make gains. It leaves Richelieu to be a likely CAQ/PQ contest, and a test of the PQ's ability to remain the alternative to the Liberals in rural francophone Quebec.
Forecast history: Was TOSS-UP (CAQ/PQ) from Zakaïb's resignation.