Griffis, who formerly worked at the Department of Commerce and as a principal at the Podesta Group, also spent a stint on President Obama's 2008 presidential campaign as communications director in South Carolina. He will serve as a senior communications advisor to Booker's campaign.

Though Booker has not yet made his Senate campaign official, he launched a campaign committee earlier this year and has been reaching out to Democrats in New Jersey for support. Hiring Griffis is the latest indication Booker is moving forward with campaign preparations.

He currently has a strong lead in most polls of the race, but a handful of other Democrats, including Rep. Frank Pallone, state Senate President Steve Sweeney and Assembly Speaker Sheila Oliver, are interested in a run.

The seat, which will be vacated by retiring Sen. Frank Lautenberg (D), is likely to stay in Democratic hands.