The NDP's online voting system has been attacked, senior party official Brad Lavigne told reporters March 24.
"The analogy I would use is that somebody was trying to break into our house, the alarm went off, and the robbers were scared away," Lavigne said in a scrum.
He stressed that the "sanctity of the vote was preserved" and that the "system was not compromised."
Lavigne initially blamed the delays on "higher than expected voter turnout."
However, the reason conflicts with the low online turnout between the second and third rounds of voting.
Less than half of the party's 131,000 members voted between the two rounds on March 24.
The invasion was described by Lavigne as a type of "denial of service" attack, in which unwanted users flooded leadership2012.ca, keeping party members from voting in the allotted time period.
The cyber-attack was traced back to two individual IP addresses.
Lavigne emphasized that that "exercising democracy takes time. One-member, one-vote is worth it."
The party hired a Spanish firm, Scytl, to manage the online voting system.
After a delay of at least one and a half hours, the results of the third leadership ballot were announced. MP Nathan Cullen placed third with 24.6 per cent of the vote. Mulcair led the pack with almost 44 per cent support, compared to Topp's 31.6 per cent.
Fourth ballot results will be announced between 8:15 p.m. and 8:25 p.m. tonight.