Cory Booker, the heavy favorite to win the New Jersey special election for Senate, launched his second TV ad on Tuesday.

Like his first ad, released two weeks ago, Booker’s new spot highlights his record as mayor of Newark. It’s a statewide ad running on cable, according to an aide.

Booker is so far the only Democratic candidate on TV, and polling continues to show him well ahead of the competition in next month’s Democratic primary. He eclipsed 50 percent again in a Quinnipiac poll out Tuesday morning.

Other Democrats vying for the seat of the late Sen. Frank R. Lautenberg are Reps. Frank Pallone Jr. and Rush D. Holt and state Speaker Sheila Oliver.

The primary will be held Aug. 13, and the special election to fill the seat for the remaining year of Lautenberg’s term is on Oct. 16.