The Nova Scotia pharmacist, a long-shot candidate who's likely to be bumped off the ballot early, announced Wednesday he's urging his supporters to make Mulcair their second choice.
"I believe that ultimately I'm the best person to lead ... but if it cannot be me, then the next-best person would be Mr. Mulcair," Singh told The Canadian Press, adding he's still "running to win."
Mulcair campaign director Raoul Gebert hailed the announcement, which follows endorsements from two former candidates, Romeo Saganash and Robert Chisholm, as a sign that "New Democrats of every stripe are uniting behind Tom's candidacy."
"Support from three other candidates in just three weeks — that speaks for itself."
However, rival camps predicted the clumsy manner in which Singh finally tipped his hand may erode the value of his endorsement —or even backfire on Mulcair.
Rival contender Peggy Nash openly questioned Wednesday whether Singh was acting on Mulcair's behalf recently in mounting "out-of-character" attacks against herself and former party president Brian Topp.
"Things are starting to add up and it's disconcerting," the Toronto MP said in an email.
"It is perfectly acceptable for a candidate to express their second choice. The problem is whether or not Mr. Singh is actively helping Mr. Mulcair."
Singh maintained he's doing nothing different from Nash or Topp, both of whom indicated as far back as early December that their second choice would be Manitoba MP Niki Ashton.
The Mulcair campaign, however, did distance itself from at least part of Singh's harsh criticism of Topp. Singh has repeatedly accused Topp of having "lied" about the impact of his tax policy on charities, of jeopardizing abortion rights and of even suggesting Jack Layton, the party's late revered leader, was not a good New Democrat.
"Martin was making a fair challenge to a blind spot in Brian's tax policy," the Mulcair camp said in an emailed statement late Wednesday.
"But we agree that this was not an appropriate way to make that point. We all make sure that we only invoke Jack's memory in the most positive and unifying way."
Singh's announcement followed several days of vehement denials that he was working in co-ordination with Mulcair — something rival camps have suspected for months.
Sukh Johal, a former western organizer for Singh, told The Canadian Press on Monday he expected Singh to endorse Mulcair as his second choice within the next day or two.
Johal, who claims to have recruited 4,500 new party members for Singh among British Columbia's South Asian community, said he was now working for Mulcair and encouraging those supporters to rank the front-runner as their second choice.
Singh's camp dismissed Johal's assertions as "a work of fiction" and denounced him as "a disgruntled ex-member of our campaign who was let go for non-performance and non-compliance."
It appeared Wednesday that Johal was no longer in charge of Mulcair's B.C. phone bank. Gebert declined to comment on Johal's status, "so as to respect his privacy."
Johal also declined comment, except to say: "As an active member of the NDP who is very passionate about the party, I will continue to engage the membership so we can build a better Canada."
In a statement posted on his website and again in a phone interview, Singh resumed his attacks on Topp, who has been his primary target for several weeks.
He said he's been reprimanded by the party for having used "unparliamentary language" when he accused Topp during a March 4 debate of having "lied" about his tax policy.
"I must tell you that I strongly object to the party trying to punish me for using unparliamentary language five days before the rule on unparliamentary language was created. And in my opinion, they're bullying my small campaign by threatening me with fines I can not afford," Singh said in the interview.
"In my mind, this is really just another tactic by Mr. Topp to distract from the fact that he did not tell the truth. And that, of course, goes along with him smearing me by calling me an attack dog of Mr. Mulcair and, really, I bring this issue up again because what it is now, it's more than just about the issue, it's about values."
Topp spokesman Jim Rutkowski declined to "dignify Mr. Singh's ongoing attacks."
"The party has already censured him for his behaviour."
With the vast majority of New Democrats expected to vote online or by mail before the March 24 convention, it's important for Singh to signal his second-choice preference now if he hopes to influence his supporters.
Under the NDP's preferential balloting system, voters rank their choices first through seventh. When a voter's first choice is eliminated, their second and subsequent choices are counted until one candidate emerges with more than 50 per cent of the votes.
Privately, strategists in several rival camps doubted the value of Singh's endorsement of Mulcair.
They predicted Singh's supporters will be confused and upset by the contradictory messages sent out over the last several days and by the treatment of Johal, who recruited many of them.
With many New Democrats turned off by Singh's tone, they mused that Wednesday's endorsement may actually backfire on Mulcair, limiting his potential for second ballot support from other camps.
Singh's repeated attacks have also created some sympathy for Topp, a longtime party strategist, and may boost his potential for second ballot growth.
In an apparently unrelated move, a Quebec MP who had initially endorsed Mulcair announced Wednesday that she has switched her support to Topp. Sana Hassainia said she was convinced by Topp's "progressive values" and his proposals to hike taxes on wealthy individuals and corporations.
But Mulcair no sooner lost Hassainia than he gained support from another MP: Newfoundland's Jack Harris. Mulcair has endorsements from 43 of the NDP's 101-member caucus, far more than any of the other six contenders.
Rival camps also questioned the Singh camp's assertion that it has signed up as many as 10,000 new members.
Joe Cressy, a spokesman for Paul Dewar's campaign, said it's "simply incorrect" to assume Singh's supporters will follow him en masse to Mulcair.
He said Dewar, the party's longtime foreign affairs critic, has strong first and second ballot support among the South Asian community. Dewar last week began running Punjabi radio ads in B.C. and Ontario.