If an election were held today, it would likely be a toss-up between the Liberals and Conservatives. But the election will be held a week from now.

What could the state of the race one week before the 2011 federal election tell us about what might happen between now and Oct. 19?

It suggests we can still expect a great deal of movement in this final week — and that momentum can be an important factor.

From the perspective of the numbers, the Conservatives were clearly en route to a majority government at this stage of the campaign in 2011. Averaging the polls conducted between April 20 and 24, the Conservatives were sitting on 38 per cent support, with the New Democrats averaging 25 per cent and the Liberals 24 per cent.

By election day, the Conservatives picked up another two points while the New Democrats gained six. The Liberals dropped five.

That was a lot of movement in a matter of days. The Liberals fell out of the race as the New Democrats closed the gap with the Conservatives by four points.

This was repeated in all of the battleground provinces. In British Columbia, the Conservatives were leading one week out with 42 per cent, versus 29 per cent for the NDP, 20 per cent for the Liberals and eight per cent for the Greens. On election night, the Conservatives and NDP were both up four points over those scores, the Liberals were down seven, and the Greens were unchanged.

The Conservatives had 42 per cent support at this stage of the campaign four years ago in Ontario, followed by the Liberals at 31 per cent and the NDP at 19 per cent. A week later, the Conservatives captured 44 per cent of the vote, with the NDP edging out the Liberals with 26 per cent to 25 per cent.

And in Quebec, the New Democrats went on a tear in the final week. They were leading in the province with a week to go with 33 per cent, with the Bloc Québécois at 28 per cent and the Liberals and Conservatives each scoring 17 per cent support. The NDP picked up another 10 points in the province in the last days, with the Bloc dropping five points and the Liberals losing three.

Momentum's the thing

This would seem to be good news for the New Democrats. Trailing the leading Liberals by 11 points (and the second-place Conservatives by about nine), the NDP needs to turn things around in the final week of this campaign to have any hope of winning. If we apply the shifts that took place in the last week of 2011 to the current polling averages, the NDP and Liberals would be tied with 29 per cent apiece, with the Conservatives ahead at 34 per cent.

But the context of the 2015 race is very different from the 2011 campaign, particularly in terms of which parties are heading in which direction.

In the final week of the 2011 campaign, it was clear that the New Democrats had the momentum. Compared with where the parties stood 10 days earlier, the New Democrats had already picked up six points in the polls by the time the final week had begun. The Liberals had dropped four. The Conservatives had hardly budged. The gains made by the NDP in that final week, then, were the continuation of the momentum it had been experiencing for over a week.

By contrast, the Liberals now appear to have the momentum. Compared with where they stood 10 days ago, the Liberals are polling about four points higher, and the New Democrats about four points lower. So if we apply the 2011 shift in the polls in the final week to the party with the momentum in this campaign, the Liberals might be heading toward a majority government.

Of course, just because something happened in the last election does not mean it will happen again. There was no significant movement like that of 2011 in the final weeks of the 2006 and 2008 campaigns.

But this does serve as a strong reminder that nothing in this election is yet settled.

CBC's Poll Tracker aggregates all publicly released polls, weighing them by sample size, date and the polling firm's accuracy record. Upper and lower ranges are based on how polls have performed in other recent elections. The seat projection model makes individual projections for all ridings in the country, based on regional shifts in support since the 2011 election and taking into account other factors such as incumbency. The projections are subject to the margins of error of the opinion polls included in the model, as well as the unpredictable nature of politics at the riding level. The polls included in the model vary in size, date and method, and have not been individually verified by the CBC. You can read the full methodology here.