The boost in support the Liberals have enjoyed since naming Justin Trudeau their new leader is similar in some ways to the honeymoon experienced by Mr. Trudeau's predecessors. But in its duration, size, and consistency, it is very different.

Both Michael Ignatieff and Stéphane Dion had surges in support in the months after they claimed the party's top job, and both leaders managed to displace the governing Conservatives in national voting intentions for some time. But neither was able to sustain their lead for longer than a few months, and they were similarly unable to consistently poll ahead of the Tories by more than a handful of points. Both met eventual defeat in their first electoral test.

Mr. Trudeau's honeymoon, however, appears to be something different.

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Under his leadership, the Liberals have held a lead over the Conservatives for five months running from April to September. Under Mr. Ignatieff, the Liberals were ahead of the Tories for a period of a little over four months, from mid-March to the beginning of August in 2009. But this lead was not immediate, as Mr. Ignatieff took over as interim leader in December, 2008, with his leadership being made permanent in May, 2009. It took him about three months to pull the Liberals out of the trough they had fallen into during the coalition affair.

Mr. Dion's honeymoon was even shorter, lasting only about two months from his leadership victory in early December, 2006, to the middle of February, 2007.

Paul Martin's tenure was entirely unlike those of his successors. He came into the Liberal leadership at a time when the party was in power and when it was routinely polling at just under 50 per cent against a divided opposition. But the merger of the Canadian Alliance and Progressive Conservatives and the emergence of the sponsorship scandal put a significant dent in Liberal support.

From a lead of 30 points or more in the months before Mr. Martin replaced Jean Chrétien, it dropped to single digits in a matter of months. Mr. Martin was at 51 per cent at his peak about a month after becoming Prime Minister in November, 2003. The Liberals plummeted to 37 per cent about three months later. However, Mr. Martin was able to win his first election as leader in 2004.

The size of the increase in support for the Liberals under Mr. Trudeau is significantly larger than the surges experienced by his predecessors. Under Mr. Dion, the Liberals went from around 28 per cent a few months before the 2006 leadership race came to a close to 36 per cent in the first month after his victory. Mr. Ignatieff boosted the party from the 26 per cent it took in the 2008 election to 35 per cent at his peak in April-May, 2009.

But Mr. Trudeau took the party from around 23 per cent support four months prior to his victory to 38 per cent in the two months after he became leader. Whereas Mr. Ignatieff and Mr. Dion boosted their party's support from the previous election by a handful of points, Mr. Trudeau had doubled it.

The lead Mr. Trudeau has enjoyed over the Conservatives is also significantly larger. In the months immediately after become leader, the Liberals moved 9 to 10 points ahead and are currently about four points in front. Mr. Ignatieff never managed a lead larger than an average of four points for any period of time and Mr. Dion's lead was never larger than three points on average. For Mr. Trudeau, his zenith represented a 31-point swing from the last election, compared to a 15-point swing for Mr. Ignatieff at his best and a nine-point swing for Mr. Dion.

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The consistency of the Liberal lead shown in the polls is particularly marked. Mr. Trudeau has led in 19 of 20 national polls in the five months since becoming leader and by an average of six points. When Mr. Ignatieff did move ahead roughly three months after becoming interim leader, he led in 24 of 31 polls in the four months during his time in the sun, and by an average of two to three points. Mr. Dion led in only 12 of the first 16 polls after his leadership victory to the middle of February, and by an average of just one to two points.

But there are some other important differences in Mr. Trudeau's honeymoon and those of his predecessors. The unusual nature of Mr. Martin's first months as leader has already been noted. Mr. Dion was the surprise winner of a leadership contest and became Official Opposition leader in a minority Parliament. Mr. Ignatieff's first months were marred by the public's reaction to the bumbling of the coalition affair by Mr. Dion. And Mr. Trudeau won a drawn-out leadership race in which his victory became a foregone conclusion long before it was made official. And he has the benefit of starting from a very low base of support in a majority legislature, where he has the time to get comfortable in the job and where the stakes are low.

Though Mr. Trudeau's leadership honeymoon does seem to be quite different from those of his predecessors, that does not mean that he will avoid their fate. But comparisons to the ill-fated polling bubbles enjoyed by past Liberal leaders should provide no comfort to Conservatives or New Democrats – this one is something different, at least for now.

Éric Grenier writes about politics and polls at ThreeHundredEight.com.