Montgomery County Council President Roger Berliner plans a run for county executive. (Gerald Martineau/The Washington Post)

Montgomery County Council President Roger Berliner announced Thursday that he will formally enter the 2018 Democratic primary for county executive next week.

Berliner (D-Potomac-Bethesda), a three-term incumbent, becomes the third council member to join the race alongside George Leventhal (D-At Large) and Marc Elrich (D-At Large). All are ineligible to run for council again under a charter amendment that limits council members and the county executive to three consecutive terms. Incumbent County Executive Isiah Leggett (D) also faces term limits.

Berliner will hold his kickoff event on Wednesday evening in North Bethesda.

Other possible Democratic candidates include former Council member Mike Knapp and wine executive David Trone.

Robin Ficker, who spearheaded the term limits campaign, is a Republican candidate for executive.