In a speech to his caucus, Mulcair takes credit for forcing the Tories to make changes to their electoral reform package, Bill C-23.
On Friday, after weeks of insisting there was nothing wrong with the bill, Democratic Reform Minister Pierre Poilievre announced that portions of the legislation would be deleted or amended.
The bill had been criticized by everyone from the current and former chief electoral officers to elections experts from across the country.
The government says it will remove a requirement for all voters to show residency identification in the next election.
Voters will now be allowed to sign an oath attesting to their residence, but must still provide at least some form of personal identification.
The government is also removing a provision that would have allowed parties to contact former donors during election periods without incurring an election expense under their campaign cap.
Chief Electoral Officer Marc Mayrand had characterized that as a huge spending loophole that would be unenforceable.
Mulcair says it was his party's push for changes to the legislation, threats of legal action and a massive petition against the bill that forced Poilievre to blink.
"We said we'd join democrats of every stripe to fight this bill in the courts, if we had to," Mulcair told New Democrat MPs.
"And thanks to our hard work, Conservatives are now saying they'll back down. We'll wait to see the fine print."
Among the other changes to the legislation is a recasting of a restriction on how the chief electoral officer can communicate with people.
While Elections Canada will still have to focus its advertising on how, when and where to cast a ballot, the chief electoral officer will be able to speak publicly about any "anything he wants," Poilievre said Friday.