Indiana's three U.S. Senate candidates will face off in the first debate of the general election campaign .
Democratic Sen. Joe Donnelly, Republican former state Rep. Mike Braun and Libertarian Lucy Brenton will take the stage Monday night at the Purdue University Northwest campus.
The race is one of the most closely watched in the U.S. and could determine which party controls the Senate next year.
Braun and Donnelly are neck-and-neck in recent public opinion polls.
The debate will be moderated by longtime Indiana broadcaster Anne Ryder.