By-Election Barometer

By-elections are the only electoral tests that parties face between elections. But being hyper-local, they can be unpredictable. The By-Election Barometer serves as a measure of what might be expected in by-elections and of what actual polls are showing, in addition to providing a basis for comparing expectations to results.

A record of forecasts vs. results can be found below - the barometer has only made the wrong call twice in 40 federal and provincial by-elections since 2012, for an accuracy rating of 95%.

The first error, in the Newfoundland and Labrador riding of Virginia Waters, was in a by-election won by just 40 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'.

For the second error, the Progressive Conservatives won the Alberta riding of Calgary West by 2.8 points over Wildrose, who were favoured. In the model, Wildrose was given a 65% chance of winning, with the Tories at 35%.

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.

Upcoming By-Elections

By-elections are scheduled 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.

The untimely death of former finance minister Jim Flaherty has left the riding of Whitby-Oshawa vacant. It will be filled in a by-election on November 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.

A poll done by Forum Research on October 27 and interviewing 894 residents of the riding gave Pat Perkins of the Conservatives 41% support, against 32% for the Liberals' Celina Caesar-Chavannes and 15% for the NDP's Trish McAuliffe.

Forecast history: Was a STRONG CONSERVATIVE at Flaherty's death.

As he is taking a job with the Progressive Conservative government in Alberta, Rob Merrifield has resigned his seat of Yellowhead, meaning another by-election will be held in Alberta on November 17.

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.

When Terry French announced he would be resigning his seat of Conception Bay South, it made him only the latest high-profile PC MHA to throw in the towel.

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.

Finance Minister Charlene Johnson decided to leave politics, leaving Trinity-Bay de Verde empty.

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.

Tom Marshall has resigned from politics on a high, leaving as the Premier of Newfoundland and Labrador. And a popular one at that - though his party was trailing in the polls at some length, voters still seemed to approve of the job Marshall was doing.

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, became LIKELY PC on October 31.

Cabinet minister Tim McMillan has resigned to take a job in the private sector, leaving Lloydminster vacant.

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.

NDP MLA Frank Whitehead resigned his seat of The Pas in May, meaning the riding is due for a by-election soon.

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.

Élaine Zakaïb may be going from one sinking ship to another, resigning from the PQ caucus to try to save the retail chain Jacob. That leaves Richelieu vacant.

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, became TOSS-UP (PQ/CAQ) on October 31.