By Steve Holland
DES MOINES, May 16 (Reuters) - A debate over the Iraq war triggered by Jeb Bush's wobbly response to questions about it spilled into a major gathering of Republican 2016 U.S. presidential hopefuls on Saturday, reflecting divisions about whether the conflict was worthwhile.
The forum sponsored by the Iowa Republican Party was the biggest gathering of 2016 rivals in Iowa to date as the presidential race picks up speed in the state that early next year holds the first nominating contest on the road to the election in November.
The threat posed by Islamic State militants who have taken over large swathes of Iraq and Syria was a dominant theme on a day U.S. officials said a raid by U.S. commandos in Syria had killed a top leader of the militancy.
Former President George W. Bush, who launched a U.S.-led invasion in Iraq in 2003, was defended by his brother, Jeb Bush, the former Florida governor who is likely to join an array of politicians vying for the Republican nomination.
Jeb Bush spent all week on the defensive after telling a Fox News interviewer that he would have authorized the invasion if he had been armed with today's intelligence. After criticism, he disavowed the remark, but said his loyalty to George W. is strong.
Noting that he is the son of former President George H.W. Bush and Barbara Bush, Jeb Bush told the Iowa gathering:
"Some of you may know that W.'s my brother. I'm proud of that, too. Whether people like that or not they're just going to have to get used to it," he said.
Kentucky Senator Rand Paul, a libertarian-leaning Republican with an isolationist streak, questioned whether the Iraq war was worth it given the rise of Islamic State, also known as ISIS.
"We have to question: Is Iraq more stable or less stable since (Iraqi leader Saddam) Hussein is gone? Is there more chaos or less chaos?" he said. "Is ISIS more of a threat now because of the instability?"
Other Republicans blame the rise of Islamic State on the failure of Democratic President Barack Obama to leave a post-war contingent of U.S. troops in Iraq. George W. Bush launched the war based on intelligence that said Iraq possessed weapons of mass destruction, which were never found.
South Carolina Senator Lindsey Graham, who turned in one of the most warmly received performances of the night, provided a counter-point to Paul. He defended the war and George W. Bush's decision to prosecute it.
"All I can say is that President Bush, W., had the same information everybody else in the world did and made the best decision he could and if anybody thinks Saddam Hussein was a good guy, they need to go back in time and check out the facts," said Graham. "I'm glad he's dead."
Addressing himself to military veterans in the crowd, Graham said: "If you fought in Iraq, it worked. It's not your fault it's going to hell. It's Obama's fault. You did your job."
Other Republicans candidates or potential candidates focused on Islamic State as a growing threat that must be challenged.
"They want to bring back a 7th century version of jihad. So here's my suggestion. We load up our bombers and we bomb them back to the 7th century," said former Pennsylvania Senator Rick Santorum. (Reporting By Steve Holland; Editing by Frances Kerry)