By Zack Colman - 07/24/13 02:23 PM EDT
Holt faces an uphill battle to secure the Democratic nomination ahead of the October special election to replace the late Sen. Frank Lautenberg (D-N.J.). The Democratic field includes Newark Mayor Cory Booker, who is the favorite, and fellow Rep. Frank Pallone Jr. (D-N.J.).
Chu, also a physicist, left the Obama administration earlier this year to take a faculty position at Stanford University.
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