The New Democrats' rise to Official Opposition status in 2011 was sudden and euphoric, its fall back to third-party status traumatic.

Nevertheless,Tom Mulcair's electoral performance in 2015 ranks positively against those of NDP leaders who preceded him.

However, the party's concentration of support in Quebec masks regional weaknesses that make Mulcair look much less impressive when stacked up against his predecessors.

Mulcair is facing new pressure this week ahead of the party's convention, which will be held from April 8 to 10. Calls for "renewal" came in an open letter Tuesday from Quebec New Democrats. During a news conference hours later, NDP MP and former leadership rival Niki Ashton declined to answer directly whether she would support Mulcair at the Edmonton convention.

A vote on holding a leadership review will take place at that gathering.

Malaise has set in among some elements of the party membership since the NDP's disappointing election results last year. The New Democrats started the campaign leading in the polls, only to be delivered one of the worst defeats ever suffered by a federal party in Canada.

The scale of the NDP's disappointment was amplified by the heights from which the party began the campaign.

But how does Tom Mulcair stack-up against past NDP leaders in terms of the actual results of the vote?

Overall, Mulcair's numbers were high by the party's standards. The NDP's vote share of 19.7 per cent was the fourth-best the party had ever managed in its 18 election campaigns. The final tally of 44 seats was its second-best performance, though in terms of seat share (13 per cent) it was third overall. 

Best electoral performance by NDP leader - seat share

Best performance by NDP leaders by seat share. (CBC)

In 1988, Ed Broadbent won 43 seats in a smaller House of Commons, for a seat share of 14.6 per cent.

Mulcair has only been bested at the ballot box, then, by Jack Layton and Ed Broadbent. In the pantheon of NDP leaders, that puts him in good company.

Mulcair's regional weaknesses

However, Mulcair was greatly helped by the party's relatively strong showing in Quebec: 25.4 per cent of the vote and 16 seats, the second-best performance for the party in the province. By comparison, every other leader except Layton averaged less than 10 per cent support in Quebec.

However, his results outside of Quebec were not nearly as strong.

​In British Columbia, Mulcair's numbers rank him 14th out of 18 elections on vote share, and tied for seventh on seat share. The only previous leaders he surpassed were Alexa McDonough and Audrey McLaughlin.

Mulcair ranked 14th on vote count in Saskatchewan and ninth on seat share. Every other leader has taken a larger share of the vote in Saskatchewan in at least one election. Mulcair's NDP took three seats in the province, though, which was better than Layton ever did — he was shutout every time.

In Manitoba, Mulcair's share of the vote was the worst the party has ever done, and in winning two seats Mulcair only did better than McLaughlin in 1993. Perhaps this partly explains why Ashton, who represents a northern Manitoba riding, was unwilling Tuesday to throw her support behind Mulcair continuing as leader.

More significant were Mulcair's results in Ontario. The NDP has never done particularly well in the province — Layton's 2011 results of 25.6 per cent of the vote and 22 seats was the best the NDP ever recorded. 

But Mulcair ranked 14th on vote share and was tied for 13th on seat share after capturing 16.6 per cent of the vote andeight seats in Ontario. Again, that put him only ahead of McDonough and McLaughlin.

As the NDP did not win a seat in Atlantic Canada, that puts him at the bottom of the regional list on that score. But he is joined by other leaders there, as the NDP only won seats in New Brunswick and Nova Scotia in about half of its elections, only three times in Newfoundland and Labrador, and never in Prince Edward Island.

Mulcair had an above-average performance on vote share in the region outside of Nova Scotia, ranking him as high as first in P.E.I. and as low as sixth in New Brunswick.

More or less than the sum of its parts?

Whether any of this matters will be decided by NDP members next month. There are multiple ways for them to interpret the numbers.

On the one hand, Mulcair led the party to a historically impressive showing. In terms of the national results, it was the best performance ever recorded by a rookie NDP leader and one of the strongest showings by the party. Mulcair managed to secure a large portion of the party's gains in Quebec, and put up respectable seat numbers in British Columbia and vote totals in Atlantic Canada.

On the other hand, the New Democrats were flirting with forming government as they have seldom done before. The party was leading in the polls with only weeks to go before the final vote.

And though Mulcair did do well in Quebec by the NDP's past standards, the less impressive performances in key provinces such as Manitoba, Ontario, and Nova Scotia highlighted the disparity in Mulcair's support in different parts of the country.

Can the NDP survive without a broader base from coast to coast?

If 2011 had never happened, few New Democrats would be looking at Mulcair's electoral results in 2015 with anything but hope and optimism. However, it is hard to ignore the outcome of that historic election and its missed opportunity.

For many members, the results of 2015 pale in comparison with what might have been, regardless of how past leaders have performed. But will those members carry the day in Edmonton and topple Tom Mulcair?

How does Mulcair stack up against NDP predecessors?3:57