Two long-serving Democrats in the New Jersey Senate are facing serious primary challenges.

Senator Ray Lesniak (R) (Dino Flammia, Townsquare Media)

Sen. Nia Gill of Montclair is being challenged by President Barack Obama's former adviser Mark Alexander in the 34th legislative district in Essex and Passaic counties. Gill has outraised Alexander slightly.

Sen. Ray Lesniak of Elizabeth is in a race against Roselle Board of Education President Donna Obe. Their fight is over representation of the 20th district, which includes the municipalities of Elizabeth, Hillside, Roselle and Union, all in Union County.

Gov. Chris Christie, his challenger and most of the 120 state legislators up for re-election this fall will skate through the June 4 primary without facing serious challenges.

In all, six of 40 incumbent senators and a handful of Assembly members have opponents in the primary.