Rep. Rush Holt (D-N.J.), an underdog U.S. Senate contender in New Jersey, has tapped journalist Glenn Greenwald for an online town hall meeting he is hosting Tuesday, his campaign announced Monday.

Greenwald, a columnist and blogger for London's Guardian newspaper, was first to report the National Security Agency's sweeping telephone surveillance effort in June. He expressed his support for Holt and -- dinged his leading opponent -- in a tweet earlier this month.

"Anyone concerned about mass spying or Wall-St-controlled crony capitalism candidates (Cory Booker) can back Rush Holt," Greenwald tweeted.

Holt is a sizable underdog in the Democratic Senate primary, which is just 15 days away. Polls show Booker, the mayor of Newark, in complete control of the race. Holt, who holds a PhD in physics, has embraced the role of quirky underdog, while seeking to underscore his liberal record and cast himself as a champion of civil liberties.

Joining Greenwald in Holt's "Geek Out Live" online town hall event will be former Energy Secretary Steven Chu, a quartet of  biology and energy experts, and Carnegie Institute President Richard Meserve. The event is being billed by Holt's campaign as a meeting that "will connect voters across New Jersey and around the country with major thought leaders to talk about the challenges facing America."