Rep. Rush Holt said the race for U.S. Senate in New Jersey is no different than previous tough campaigns he's been in and won.
The Princeton-area congressman launched his campaign for the Democratic nomination with an introductory video and website Wednesday.
Holt is seen as an underdog to Newark Mayor Cory Booker, who is better known, and Rep. Frank Pallone, who has raised more money.
Voting records, not celebrity, will define the race, Holt said.
The astrophysicist has a 100 percent pro-environment voting record and once beat a supercomputer named Watson at "Jeopardy."
The primary is in eight weeks. The seat became available with the June 3 death of 89-year-old Frank Lautenberg, who had been the oldest member of the Senate.