The Newark mayor is known for his prolific presence on Twitter. He interacts with constituents via the social media platform, and will re-tweet kind words from those he's helped.
Booker is likely to run for Senate, and has already set up his campaign committee. Sources say he is working behind the scenes to shore up support and raise funds.
Rivera has expressed interest in running for retiring Sen. Frank Lautenberg's (D-N.J.) seat in 2014, though he hasn't made any definite plans.