Mandel, who served as party leader for 15 months, is resigning his leadership to pursue his role as Chancellor at Concordia University.
“To serve as the leader for the past 15 months has been a tremendous honour,” Mandel said in an email to party members. “The results were not as we had hoped but I believe we have broken new ground by gaining the support of over nine per cent of the popular vote.
“I am grateful for all the support and thoroughly enjoyed travelling the province making connections.
“Although I’m stepping aside as leader, I will continue to be involved in the party. I also look forward to quality time with my family.”
Mandel will resign effective June 30.
The Alberta Party ran candidates in all 87 ridings during the 2019 Alberta provincial election, but was ultimately shut out from the legislature after securing just 9.1 per cent of the popular vote.
Support for the party did grow under Mandel’s tenure as leader, gaining 171,995 compared to 33,221 in the 2015 provincial election, which was just 2.2 per cent of the popular vote.
LISTEN BELOW: Stephen Mandel joins the 630 CHED Afternoon News
“Mr. Mandel is one of the hardest working leaders this province has seen since Peter Lougheed. His commitment to the Alberta Party was immense and widespread,” Alberta Party president Conrad Guay said. “Mandel has left the party with the tools needed to move forward. We thank him for his hard work and wish him well in his future endeavors.”
Mandel served as Edmonton’s mayor from 2004 to 2013.
He went on to serve as Minister of Health in Jim Prentice’s cabinet until the Progressive Conservatives were defeated in the 2015 election.
Mandel announced his intentions of running for the leadership of the Alberta Party in January 2018, and succeeded Greg Clark as leader in February 2018 with 66 per cent of the vote.
WATCH: Alberta Election 2019: Alberta Party Leader Stephen Mandel ‘very proud’ of party’s efforts
According to an email sent to party members on Friday, the Alberta Party is now working to recruit an interim leader, who will be appointed by the party’s board.
READ MORE: By the numbers: Alberta election 2019
The party said multiple candidates have expressed interest, but did not disclose who.
Details regarding a leadership race are expected to be set at the party’s next annual general meeting, which has yet to be scheduled.