Senator Ted Cruz of Texas, who is leading some polls in Iowa, which holds the first presidential nominating contest on February faulted Obama for not mentioning Iran detaining 10 US sailors earlier this week during his State of the Union Address on Tuesday.
"It was heartbreaking," Cruz said, referring to images of the detained American service members with their hands on their heads.
New Jersey Governor Chris Christie said watching the president's address was like watching "story time with Barack Obama."
Related reading
Obama speech knocks Trump, voices hope
The president gave his final State of the Union address on Tuesday and offered an optimistic vision of America's future as a contrast to the Republican field of candidates trying to replace him.
Without naming him, he singled out Republican front-runner Donald Trump for calling on the United States to ban Muslims temporarily from entering the country.
Trump doubled down on that call on Thursday.
The sixth Republican debate, at the North Charleston Coliseum in the swing state of South Carolina, takes place at a tense time for the Republican field with the clock ticking toward February 1 in Iowa, which holds the first contest in the race to choose the party's nominee for the November 8 general election.
The top seven candidates ranked by Republican voters took part in the debate: real estate businessman and reality TV star Trump, Texas Senator Cruz, Florida Senator Marco Rubio, retired neurosurgeon Ben Carson, former Florida Governor Jeb Bush, New Jersey Governor Chris Christie and Ohio Governor John Kasich.
Trump and Cruz have been friendly over the past year, until now.
Cruz has taken the lead in some polls of Iowa Republican voters.
A victory there could propel him higher in the national race.
A Reuters/Ipsos rolling national poll on Jan. 12 showed Trump had 39 percent of the vote, Cruz 14.5 percent, Bush 10.6 percent, Carson 9.6 percent, while 6.7 percent favoured Rubio, once viewed by the Republican establishment and many donors as a rising star.
In an earlier debate of low-polling candidates, Republicans Carly Fiorina, Mike Huckabee and Rick Santorum largely focused their criticism on Democrats rather than each other.
Fiorina, the former Hewlett-Packard CEO who was demoted from the main stage because of faltering poll numbers, dominated the so-called "undercard" debate with a series of one-line zingers, one of them aimed at Democrat Hillary Clinton over her prior marital strains with Bill Clinton, the former president.
"Unlike another woman in this race, I actually love spending time with my husband," she said.
Share
