With only three days left to register, just 89,000 had registered by Monday evening.
Members and supporters must register by Thursday in order to be entitled to vote.
The party boasted last week that 294,000 people had signed up over the course of the leadership contest.
Most signed up free of charge, taking advantage of the party's new supporter class, which was intended to broaden the Liberal base and engage more than just card-carrying, dues-paying members in the leadership vote.
While only a fraction so far have bothered to take the next step, spokeswoman Sarah Bain says the party is pleased with the number who've registered.
She said the party has seen "a healthy surge" in registrations as the Thursday deadline looms.
However, the Trudeau team — which has boasted of signing up as many as 165,000 supporters — has written the co-chairs of the leadership vote rules committee, expressing concern about numerous technical glitches that are preventing people from registering.
Trudeau representative Cyrus Reporter asks that registration be extended by one week and that the party "engage additional resources" to create a "high intensity phone bank" to contact anyone who has not yet registered.
It's vital that new supporters' first experience with the party be rewarding if there is to be any hope of them eventually becoming full-fledged party members, donors or election volunteers, Reporter argues.
"In effect, these new recruits are 'kicking the tires' of our party," he writes.
"Unfortunately, unless action is taken, we will have an unacceptable number of supporters who will not be able to participate in the activity that they have signed up for: voting for our new leader."
Reporter identifies a particular problem with the "tens of thousands" of supporters — in fact, the Trudeau team says its more than 100,000 — who signed up without providing email addresses. He says only five per cent of those people have registered so far.
The party had to use regular mail to send registration forms to people without email addresses. According to Reporter:
— The first batch of mailings included incorrect numerical codes that didn't allow recipients to register.
— The final mailing was sent only last Thursday and Friday and many people still haven't received their registration forms. Canada Post has told the Trudeau team that supporters outside Ontario won't receive the forms until one or two days before Thursday's registration deadline.
— English-speaking supporters in Quebec have received registration packages in French.
Reporter says individuals who did provide email addresses have also experienced some problems. For instance, some have found there is no "submit" button on their online registration form; the party has told them to update their browsers, with minimal advice on how to do that.
The Trudeau team submitted help requests on behalf of 124 supporters who did not receive an online registration email from the party, although they have valid email addresses.
As well, Reporter says the camp has received numerous emails from people who registered but did not receive confirmation. After reviewing the party's registration list, he says about half of these individuals are not registered "even though they thought that they were."
The Ontario wing of the party has also asked that the registration period be extended.
Bain said it's up to the party's board and leadership committee to determine if an extension on registration is warranted or feasible. As far as party officials are concerned, Thursday "is a major deadline," she added.
Regardless of how many actually end up voting, interim Liberal leader Bob Rae last week said the supporter experiment has already been a success. It's added thousands of new names and contact information to the party's database, which is used to tap donors, recruit volunteers and target sympathetic voters during elections.
Still, the failure to register by two-thirds of supporters thus far suggests they have little attachment to the party, likely won't vote for the next leader during the week of April 6 and may not prove to be particularly useful to the party after that.
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