Newark Mayor Cory Booker (D) is widely expected to run in the special election for the late Sen. Frank Lautenberg's (D-N.J.) seat this October.

But in order to do so, he will have to break a pledge.

Back in December, Booker said in a video announcing his Senate exploratory committee -- in no uncertain terms -- that he would serve out the remainder of his tenure as mayor, which ends in mid-2014.

“Let there be no doubt: I will complete my full second term as mayor of Newark, New Jersey," Booker said back then. "And as for my political future, I will explore the possibility of running for the United States Senate in 2014.”

The language also appears on his campaign Web site, to this day.

At the time, Booker faced some reports that questioned his stewardship of the city, and his statement that he would serve out his term seemed aimed more at making clear that he wouldn't run against Gov. Chris Christie (R) in 2013.

But today, it's putting Booker in an awkward position, in which he will have to break his pledge, unless he wants to let some other Democrat potentially get a leg up on him in the 2014 election by winning the seat this year.