Cory Booker's experience as mayor of Newark, N.J., would be a big advantage in Washington, Maryland Gov. Martin O'Malley said.
O'Malley is campaigning for Booker throughout the day in New Jersey.
The U.S. Senate candidate will meet up with O'Malley after a debate Thursday night in Newark.
The Maryland governor, meanwhile, is attending campaign events in Trenton and Paterson.
He endorsed Booker in June.
O'Malley, who is considering a 2016 presidential run, is the finance chairman for the Democratic Governors Association.
He deflected questions about his own political aspirations while promoting Booker at a senior housing complex in Trenton.