| SIMI VALLEY, Calif.
SIMI VALLEY, Calif. Jeb Bush, once a heavy favorite for the Republican nomination, will try to energize his presidential campaign on Wednesday when he goes into a prime-time debate where Donald Trump looms large.
The former Florida governor, an establishment Republican, has been overshadowed by Trump's bomb-throwing rhetoric in the contest to become the party's candidate for the November 2016 presidential election.
A Bush campaign aide said Jeb will focus on his “hopeful, optimistic vision” for how he would lead the country and that if an opportunity presents itself to contrast himself with Trump, he will take it. “He’s not going to shy away on the Trump front,” said the aide.
Reuters/Ipsos opinion polling has Trump leading among Republican voters with 32.2 percent. Retired neurosurgeon Ben Carson is second at 15.8 percent.
Bush, the younger brother of former President George W. Bush, is in third place on 9 percent as his campaign struggles to take off.
Eleven candidates will be on stage for the debate, at the Ronald Reagan Presidential Library in Simi Valley, due to start at 8 p.m. ET (0000 GMT Thursday).
Trump has mocked Bush as a "low-energy" candidate, but the well-funded former governor has begun to hit back and has vowed not to be passive at the debate.
"If someone comes at me, bam!, I'll come back at 'em," he said at a campaign event in New Hampshire last week.
A Super PAC supporting Bush launched an ad on its YouTube channel this week accusing real estate magnate Trump of being "in a very dark place."
Wisconsin Governor Scott Walker is another conservative favorite who is now trailing Trump. He is at seventh place in the Reuters/Ipsos poll, and a Gallup survey shows that he is unfamiliar to 44 percent of Republicans even though he was often mentioned by pundits only a few months ago as a contender.
"Walker’s decline really kind of shocks me,” said Alan Abramowitz, professor of political science at Emory University. “I thought he was well positioned to at least make it to the final three or four.”
Trump, who dominated the first main Republican debate in Ohio last month, on Monday dismissed possible attacks from rivals this time around.
"I hear they are going after me. Whatever. Whatever," he said at a campaign rally in Dallas.
The debate, staged next to the retired Air Force One aircraft used by Reagan, is being hosted by CNN.
It will be the first time Trump has been on stage with former Hewlett-Packard Chief Executive Carly Fiorina, whom he insulted in recent weeks with a comment about her face.
People are “very interested to see not just how she performs in the debate as a whole but how she decides to directly engage Mr. Trump,” said Matt Strawn, former chairman of the Iowa Republican Party.
A CBS News/New York Times poll said 63 percent of Republican voters had not yet decided whom to support.
A poor showing by Bush on Wednesday could just be a blip that might not prove fatal, said Steven Brams, professor of politics at New York University. “The debate tonight will not be do or die,” he said.
Also debating will be Ted Cruz, Marco Rubio, Mike Huckabee, Rand Paul, John Kasich and Chris Christie.
Before the prime-time encounter, Rick Santorum, Bobby Jindal, George Pataki and Lindsey Graham participated in the 'undercard' debate of those candidates who did not poll strongly enough to qualify for the main event.
Jindal, the Louisiana governor, and Pataki, the former New York governor, led the charge against Trump.
"Let's stop treating Donald Trump like a Republican," said Jindal. "He's not a conservative. He's not a liberal. He's not a Democrat. He's not a Republican. He's not an independent. He believes in Donald Trump."
Pataki, who has vowed not to support Trump if he is the nominee, insisted Trump would not get that far,
"Donald Trump is not going to be the Republican nominee, period. I guarantee you that," said Pataki.
For more on the 2016 presidential race, see the Reuters blog, “Tales from the Trail”. (here)
(Writing by Alistair Bell; Additional reporting by Alana Wise, Michelle Conlin and Luciana Lopez; Editing by Steve Orlofsky)