New Jersey Sen. Cory Booker isn't running for office this Election Day -- but he was still running. Through traffic.

Booker spent part of his Tuesday in the rain talking to passing motorists, wielding a sign telling surprised New Jerseyites to vote and making some personal pitches, too -- Booker's Senate colleague, fellow Democrat Robert Menendez, faces a tough re-election fight.

Booker, who in September compared himself to Thracian gladiator Spartacus, tweeted video showing him running around a rainy New Jersey street, carrying a sign that read: “Don’t forget to vote today.”

“Don’t forget to vote,” he echoed to passersby, who beeped their car horns. “We need you, we need you.”

The video showed him putting his hand through car windows, apparently shaking hands with those in the car.

Booker is not up for re-election in New Jersey on Tuesday; but Menendez, the state's senior senator, faces a surprisingly fierce battle in the blue state against Republican challenger Bob Hugin.

Menedez was wounded when he was found to have broken Senate ethics rules about receiving gifts -- although a federal bribery case against him resulted in a mistrial last year.

Hugin has been outspending Menendez by a 3-1 margin, but Menendez has been boosted by the Senate Democrats’ super PAC, which announced a $2.8 million increase in funding to Menendez last week, on top of another $3 million it recently shifted to New Jersey.

CORY BOOKER CLEARED TO RUN FOR PRESIDENT, SENATE SIMULTANEOUSLY AFTER NEW JERSEY ENACTS 'CORY'S LAW'

Booker is rumored to be considering a 2020 presidential run. Gov. Phil Murphy signed a bill Thursday allowing any member of the U.S. House or Senate from New Jersey to run for those offices in addition to pursuing the White House.

Fox News’ Lukas Mikelionis contributed to this report.