In a statement posted today on his blog, Lamrock says his work as a lawyer and family commitments make it hard to put in the time needed for an all out, sustained campaign.
The 41-year-old former politician joined the race in March and had been gathering input from Liberals around the province.
He is throwing his support behind Moncton lawyer Mike Murphy, who also served in the cabinet of former premier Shawn Graham.
The two other candidates in the race are Moncton lawyer Brian Gallant and farmer Nick Duivenvoorden (Dy-ven-vor-den).
The leadership convention is at the end of October.