Newark Mayor Cory Booker (D) on Tuesday released the first ad of his Senate campaign that goes after Steve Lonegan, his Republican opponent.

"He'd privatize Social Security, shut down government, ban all abortion," a narrator says of Lonegan. Booker adds, "New Jersey, we're better than that. As senator, I'll take on the tough problems."

With 15 days left until the special election, Booker remains a substantial front-runner, but polls show the race could be tightening. A Monmouth University poll released Tuesday shows Booker up by 13 -- down a bit from his 16-point lead in the previous poll. A recent Quinnipiac University survey showed him up 12.

Lonegan, the former mayor of Bogota, N.J., has already gone negative against Booker over the airwaves. He recently released a spot hitting Booker for supporting Obamacare, which Lonegan opposes.