Success for Selinger would mean securing the job he already holds.
Selinger is expected to file his nomination papers at 12:15 p.m. at the NDP provincial office on Portage Avenue, according to his leadership campaign.
The premier is the third person to enter the race for the NDP leadership.
Former minister for jobs and the economy and one of five rebel cabinet ministers Theresa Oswald first entered the race, followed by Steve Ashton, who resigned as transportation minister leading up to it.
Selinger will stay on as premier during the leadership race, which is scheduled to take place at the NDP convention on March 8.