GOP presidential debate at the Reagan Library

Candidates Scott Walker and Carly Fiorina walk onstage at the start of the GOP debate at the Reagan Library in Simi Valley.

Republican presidential candidate Ben Carson, left, and Donald Trump shake during the GOP debate at the Reagan Library.

Donald Trump

Republican presidential candidates Donald Trump and Jeb Bush spar early in the GOP debate at the Reagan Presidential Library in Simi Valley.

Republican presidential candidates shake hands at the end of the GOP debate at the Reagan Library in Simi Valley.

A jubilant Reince Priebus, chairman of the Republican National Committee, walks the spin room after the debate.

Republican presidential candidates Donald Trump and Jeb Bush high-five during the GOP debate at the Reagan Library in Simi Valley.

Republican presidential candidate Donald Trump joins Arnold Schwarzenegger after the GOP debate at the Reagan Library.

Candidate Ben Carson is surrounded by media in the spin room after the GOP debate at the Reagan Library.

Candidate Donald Trump makes his way through a media scrum as he tries to exit the spin room after the debate.

Air Force One serves as a backdrop for the Republican presidential debate held Wednesday at the Ronald Reagan Presidential Library in Simi Valley.

Marco Rubio, left, and Ted Cruz

Former Governor Arnold Schwarzenegger attends the GOP debate at the Reagan Library in Simi Valley.

Donald Trump speaks during the GOP debate at the Reagan Presidential Library in Simi Valley.

Chris Christie

Rand Paul

Mike Huckabee

Carly Fiorina

Presidential candidates Ben Carson, left and Donald Trump during the GOP debate at the Reagan Library in Simi Valley.

Donald Trump and Jeb Bush talk before the 2015 Republican presidential debate held Wednesday at the Ronald Reagan Presidential Library in Simi Valley.

Republican presidential candidates on the stage before the start of the main GOP debate at the Reagan Library in Simi Valley.

Republican presidential candidates Rick Santorum, George Pataki, Bobby Jindal and Lindsey Graham, from left, after the second-tier GOP debate at the Reagan Library in Simi Valley.

Republican presidential candidate Gov. Bobby Jindal after the GOP debate at the Reagan Library in Simi Valley.

Republican presidential candidates George Pataki and Rick Santorum during the early GOP debate at the Reagan Library in Simi Valley.

CNN moderator Jake Tapper speaks at the opening of the debate at the Reagan Library.

Republican presidential candidates George Pataki, Rick Santorum, Bobby Jindal and Lindsey Graham are introduced during the first-tier GOP debate at the Reagan Library.

The first debate featured four Republican presidential candidates at the Reagan Library.

The media filing room is filled with images of Republican presidential candidate Donald Trump at the GOP debate at the Reagan Library.

Republican presidential candidate Ben Carson, front, passes a row of images of former U.S. presidents before the GOP debate at the Reagan Presidential Library in Simi Valley.

Republican presidential candidate Ben Carson talks to reporters in the media tent before the GOP debate at the Reagan Library.

Republican presidential candidate Gov. Scott Walker of Wisconsin interviews with Fox News before the GOP debate at the Reagan Library in Simi Valley.

Republican presidential candidate Gov. Scott Walker of Wisconsin after an interview with Fox News at the Reagan Library prior to the GOP debate.

A banner of Ronald Reagan greets visitors as they arrive for the Republican presidential debate at the Reagan Library in Simi Valley.

Members of the media prepare for the GOP debate at the Reagan Library in Simi Valley.

Preparations are made inside the spin room backstage at the GOP debate at the Reagan Library in Simi Valley.

Paul Raphel, a producer for Larry King’s “Kings’ Politiking,� works in a cubicle inside the spin room backstage at the GOP debate at the Reagan Library in Simi Valley.

Reporters prepare for the GOP debate at the Reagan Library in Simi Valley.

Members of the media walk through the set before the GOP debate at the Reagan Library in Simi Valley.