Supporters of front-runner Thomas Mulcair, the target of some blunt criticism from Broadbent on Thursday, say the unprecedented attack has backfired, repulsing many New Democrats who fear for the long-term unity of the party.
And they say it has made Brian Topp, Broadbent's preferred choice for leader, look desperate.
But Topp's backers believe the intervention has helped define the race, heading into the final week, as a fundamental choice between Mulcair and Topp, sidelining the other five contenders.
For his part, Broadbent insists he'll support whoever wins.
Broadbent gave a series of interviews Thursday in which he questioned Mulcair's temperamental suitability to lead the party, denounced his apparent willingness to turn the NDP into a more centrist party and accused him of taking undue credit for the party's electoral success in Quebec.
"Perhaps the Topp campaign is desperate," northern Ontario MP John Rafferty, a Mulcair supporter, said Friday.
"That was the first thing I thought when I, when I read Mr. Broadbent's comment yesterday, that perhaps the Topp camp is very, very worried. This is clearly, you know, a last-ditch attempt to gain some votes."
Rafferty said Mulcair and dark horse contender Nathan Cullen appear to be the only candidates with momentum heading into the home stretch, and "that's got to ... make for a pretty unhappy camp in the Topp camp."
The latest weekly financial returns filed by each of the candidates with Elections Canada bear out the sense of momentum for the Mulcair and Cullen camps, at least in terms of fundraising. Both raked in more than $30,000 over the past week — three time more than any of the other five contenders.
Mulcair continues to set the pace overall, having raised almost $241,000 thus far. Topp has raised $204,000, Cullen $175,000, Toronto MP Peggy Nash $167,000, Ottawa MP Paul Dewar $160,000, Nova Scotia pharmacist Martin Singh $60,000 and Manitoba MP Niki Ashton $$40,000.
Cullen has tapped the largest number of contributors — 1,624, just slightly ahead of Mulcair.
Unlike the Conservative and Liberal parties, in which leaders tend not to get involved in leadership contests after they retire, it is not unusual for former NDP leaders to endorse candidates. Broadbent endorsed the late Jack Layton in the last contest and Topp in the current race. Former leader Alexa McDonough is backing Toronto MP Peggy Nash.
But it's unprecedented for a former leader, especially one of Broadbent's iconic stature in the NDP, to openly criticize a rival leadership hopeful.
The Topp camp is hoping his stature in the party will carry weight with members, particularly NDP stalwarts.
Peter Julian, the NDP caucus chairman, defended Broadbent's right to speak out but suggested the impact of his intervention may cut two ways.
"I think he has the right to his opinion," said Julian, who has remained neutral in the race thus far.
"When Mr. Broadbent speaks, some people will have a positive reaction. Some people may feel that his remarks were not appropriate. But the reality is you have 130,000 New Democrats that are making those decisions over the course of the next few days."
Mulcair supporters on social media sites were still seething about what they consider a divisive intervention that will make it much harder to unify the party once the race is over, particularly if Mulcair wins. And some of the front-runner's strategists privately said disgusted New Democrats are actually moving to Mulcair as a result.
However, a number of New Democrat MPs, including Rafferty, played down the long-term consequences of the affair. They predicted the party will reunite once the race concludes on March 24.
"I think you'll find ... that there will be unanimity that maybe we haven't seen in the NDP for a long time, regardless of who becomes leader," Rafferty said.
"The reality is, when you look at the last six months, there's been a remarkable degree of unity in this leadership race that we haven't seen before in a major Canadian political party," agreed Julian.
"And I think we're going to come out of this leadership convention united and stronger than ever."
Broadbent told The Canadian Press on Thursday that leadership contests always leave "bitter feelings" that need to be smoothed over afterward.
"This maybe sounds kind of fatuous or self-evident but it's true. Emotional intensity often gets greater within a party when you're in conflict than it does when you're dealing with your political opponents. It's analogous I guess to the feelings that people have found in civil wars," he said.
"But then it's a task of leadership after to bring people together. That should begin right after the winning ballot takes place."
For his own part, Broadbent said he'll support whoever wins on March 24.
"I hope obviously that Brian wins but if someone else wins who has not the same strengths that I see in Brian, I hope I will turn out to be mistaken in some regard or that the candidate in question will moderate her or his behaviour," he said.
"In that respect, I'm like most other New Democrats .... I'm emotionally very engaged in this but after, I hope and plan to be able — and I'm sure I will — be able to accept the results."