Republican presidential candidates will gather in Southern California on Wednesday night to participate in a highly-anticipated debate hosted by CNN.

Like before, the debate will feature a two-tier structure: an early "undercard" forum for candidates with the lowest poll numbers and a primetime main event for the more popular candidates. Both debates will be moderated by CNN anchor Jake Tapper, with CNN political correspondent Dana Bush and conservative radio host Hugh Hewitt asking additional questions. 

Donald Trump, who has led Republican polls for more than two months, will likely be a big draw for viewers, as he made headlines after the Fox debate for clashing with moderator and Fox News host, Megyn Kelly.

While Trump has dominated the race for months, Dr. Ben Carson, a retired neurosurgeon has seen a steady surge in the polls, earning the second-place spot despite never holding public office.

Trump  and Carson will be joined on the main stage at 8 p.m. EDT by nine others:  former Florida Gov. Jeb Bush; Ohio Gov. John Kasich; Wisconsin Gov. Scott Walker; former Arkansas Gov. Mike Huckabee; businesswoman Carly Fiorina; Texas Sen. Ted Cruz; Florida Sen. Marco Rubio; and Kentucky Sen. Rand Paul. The debate is expected to end at 10 p.m. EDT.

The earlier debate, held at 6 p.m. EDT features the lower-polling candidates: South Carolina Sen. Lindsey Graham, Louisiana Gov. Bobby Jindal, former Pennsylvania Sen. Rick Santorum and former New York Gov. George Pataki.

The network determined the lineup based on an average of recent polls. While just the top ten were meant to qualify, CNN amended the rules to include Fiorina after she saw a boost in support following the Aug. 6 debate. The gathering will be held at the Ronald Reagan Presidential Library, with the stage set up next to the retired Air Force One aircraft used by the late president.

Both debates will be live on CNN, CNN International and CNN Espanol. Unlike Fox News, which hosted the first debate, CNN will be forgoing cable provider password protections for its live streams, broadcasting the debate for free on its website and other mobile platforms, the New York Times notes.

For those who prefer to listen instead of watch, a live broadcast of the debate will be available Salem Communications radio stations.

Those who want to join in conversation about the debate on social media can do so using the #GOPDebate hashtag on Twitter and Facebook