Rafizi Ramli has confirmed that he will contest the PKR deputy president's post in the August party elections.
Should incumbent Azmin Ali choose to defend his position, it would mean that the rivalry between the two, which has been simmering for years, will come to a boil.
The current PKR vice-president said he would be making a formal announcement on the matter this Sunday.
Quizzed on what motivated him to gun for number two, Rafizi described it as a contest between career politicians and reformists in PKR.