Middlesex County District Attorney Gerard T. Leone Jr. is giving “serious consideration” to running in the special US Senate race to fill John Kerry’s seat, he confirmed Saturday.

Leone, 50, said he has received encouragement from friends and political allies to jump into the Democratic primary campaign - a race that already has two Massachusetts congressmen, Edward J. Markey and Stephen P. Lynch, battling for the party nomination. The primary will be held April 30.