The joke was a clear reference to perceptions that the ambitious Newark mayor spends significant time burnishing his national image on the cable television circuit. 

Booker has announced his intention to seek Lautenberg's seat in 2014. The incumbent New Jersey senator will be 90 years old if he decided to mount a reelection bid rather than retire. But the swipe Thursday night is another signal that Lautenberg is upset with Booker's decision to publicly declare his intention to challenge the long-term lawmaker.

Still, Booker is heavily favored to take the Democratic nomination if Lautenberg decides to seek reelection. In a Quinnipiac University poll released earlier this week, Booker held a 51-30 percent lead among primary voters. More than seven in 10 say Lautenberg's age makes his work too difficult.