Pallone entered the race for deceased Sen. Frank Lautenberg's (D-N.J.) seat with a considerable fundraising advantage, posting $3.7 million in his war chest to Booker's $1.6 million.

But Booker has crisscrossed the state, and the nation, raising money for his bid, and Pallone told the Bergen Record he expects the Newark mayor to catch up to him when second-quarter numbers are released.

“I suspect on July 15 when the reports come out, you won’t see me as the guy who has the most money,” Pallone said.

The money advantage is a significant one in the short time-frame of a special, but despite Pallone's lead in fundraising, only Booker is currently running television ads in the state.

Meanwhile, Democrat Rep. Rush Holt (N.J.) has released a new Web ad in the race that features supporters, many of whom are young, speaking straight-to-camera explaining why they're backing his bid. They cite his background as a scientist, teacher, his support for math and science funding and his progressive voting record.

"I'm with Rush because I know we can win," speakers repeat three times in the video.

Holt and Pallone remain underdogs in the race against Booker, who is well-known and well-liked in the state, but polling is expected to tighten as the race heats up. The primary is scheduled for Aug. 13, and Democrats are favored to keep the seat in the Oct. 16 general.