By Lisa Richwine and Alistair Bell
LOS ANGELES/WASHINGTON (Reuters) - The Republican candidates' debate on Fox News Channel attracted 24 million viewers, more than double the prior record for a presidential primary forum, with social media data suggesting
combative billionaire Donald Trump was the main attraction.
Viewership for the raucous 10-way debate was the highest non-sports telecast in cable history, according to Nielsen data provided by Fox.
Republicans will mostly welcome the attention to mainstream candidates like Marco Rubio, the U.S. senator from Florida, and Jeb Bush, the former Florida governor, as they try to prevent a Democrat winning the White House in November 2016 for the third time in a row.
But the performance by reality TV show host Trump dominated the night. He courted controversy with the Republican establishment by refusing to rule out an independent bid for the White House and bristled when accused of making offensive remarks about women.
The size of the audience blew past predictions by media experts and was more than double Fox News Channel's previous largest audience, the 11.8 million viewers who tuned in on election night in November 2012.
"Clearly Trump was the catalyst for the audience," said Alan Schroeder, a Northeastern University journalism professor who has written extensively about presidential debates.
"When you throw in somebody like Donald Trump into a combustible formula like a live debate, it’s a very compelling thing for audiences,” he added.
Data suggested Trump was the biggest draw of the 10 candidates on the debate stage in Cleveland.
The property magnate was the most-mentioned candidate on Twitter during the event, the most discussed on Facebook and the most searched on Google, according to those companies.
Retired neurosurgeon Ben Carson was a distant second on Twitter and Facebook.
Less clear was how Trump fared in the debate itself, drawing boos from the audience at points.
In a show of hands immediately after the debate, participants in a Fox News focus group who supported Trump beforehand overwhelmingly indicated they had changed their minds about him.
They criticized his refusal to commit to backing the eventual Republican nominee - if not Trump himself - and accused him of being no more forthcoming than traditional politicians.
"I think he took out a gun and shot his campaign in the head," said Florida Republican strategist Rick Wilson.
But Trump also drew applause and cheers during the two-hour debate, and two online surveys on Friday suggested he was a winner. He had 47 percent of the votes - amounting to 42,980 clicks - on Time's website and 38 percent on Slate.com.
Neither of the surveys had a margin of error and readers outside of the United States could vote.
The polls "only tell you about the sentiment of the couple of thousand people who decide to vote on that website at that time," said Chris Jackson of Ipsos, which does polling in partnership with Reuters.
The surveys on Friday were in contrast to more reliable online polls that ask participants about their party affiliation, gender, zip code and other details to ensure the poll has a representative slice of the population.
Trump on Friday denied comments by Fox News debate moderator Megyn Kelly that he had used offensive terms in the past to describe women, including "fat pigs," "dogs" and "slobs."
"I didn't say many of those things," he told MSNBC's "Morning Joe" show. "In fact, I'm going to have somebody call up and find out where these words came from because I don't recognize those words."
The other Republicans on the stage largely avoided direct challenges to Trump, who has rocketed to the top of Republican opinion polls in the 2016 race.
Previously, the most-watched primary debate was a 2008 event that included Democrats Hillary Clinton and Barack Obama.
(Additional reporting by Susan Heavey in Washington; Editing by Leslie Adler)