* Sixth Republican debate in swing state of South Carolina
* First contest for party nomination just weeks away in Iowa
By Steve Holland and Emily Stephenson
CHARLESTON, S.C./MANCHESTER, N.H., Jan 14 (Reuters) -
F laring tempers and sharp elbows may turn a debate of seven
Republican presidential candidates into a seven-car pileup on
Thursday with tensions between Donald Trump and rival Ted Cruz
leading the way.
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 Feb. 1 in Iowa, the first contest in the race to choose
the party's nominee for the Nov. 8 general election.
"Everybody has to avoid making mistakes," said David Yepsen,
director of the Paul Simon Public Policy Institute at Southern
Illinois University. "If you mess something up in this debate
you're going to have almost no opportunity to correct it."
The 9 p.m. EST (0200 GMT Friday) debate features the top
seven candidates ranked by Republican voters: New York 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.
Nearly every candidate has had a bone to pick with one or
more of the others this week. Beyond the Trump-Cruz theatrics,
Bush has blasted Trump and Rubio, Rubio has slammed Bush as well
as Cruz and Christie, and Christie has attacked most everyone
else.
If Fox Business Channel moderators Neil Cavuto and Maria
Bartiromo focus on these disputes, the debate could be one of
the liveliest of the series.
But whether the bickering helps is questionable.
"I think the Republicans have to stop beating up each other
and let their opponents do that in the Democratic Party," said
Republican voter J.P. Marzullo of Deering, N.H.
Front-runner Trump has put Cruz, his main obstacle to an
Iowa victory, on the defensive by suggesting Cruz may not
qualify to be a candidate because he was born in Canada (to a
U.S. citizen mother and a Cuban father).
This was a change in posture by Trump on the issue, however,
after saying in an interview with ABC News last September that
he had heard that lawyers believed it was not a problem for
Cruz.
Trump and Cruz have been friendly over the past year, until
now.
Being targeted by Trump is a new position for Cruz, who has
taken the lead in some polls of Iowa Republican voters in part
by avoiding tangles with Trump.
In the Reuters rolling national poll on Jan. 12, Trump had
39 percent of the vote, Cruz 14.5 percent, Bush 10.6 percent,
Carson 9.6 percent and 6.7 percent favored Rubio, once viewed by
the Republican establishment and many donors as a rising star.
Cruz told reporters in New Hampshire on Tuesday that Trump
is relying on a judgment on the birthright question from Harvard
law professor Laurence Tribe, who Cruz described as "a liberal,
left-wing, judicial-activist" and a supporter of Democratic
Party front-runner Hillary Clinton.
"The past couple of elections we saw the Democrats thrilled
that they got the nominee they wanted to run against in the
general election, and it seems the Hillary folks are very eager
to support Donald Trump," Cruz said.
Trump, who has proved to be a master at finding a perceived
weakness in an opponent, insisted Cruz's Canadian birth violated
the U.S. Constitution's requirement that only native-born
Americans can be president.
"Sadly, there is no way that Ted Cruz can continue running
in the Republican Primary unless he can erase doubt on
eligibility. Dems will sue!" he tweeted on Wednesday.
Mudslinging abounds elsewhere in the field as a grouping of
other candidates fight to be the alternative to Trump with
battles over national security and immigration.
"Given all the attacks that are taking place and the counter
attacks, I think it will be a more lively debate than we've seen
at this point," said Eric Fehrnstrom, who was a top adviser to
2012 Republican nominee Mitt Romney. "Donald Trump is still in
complete command and the race is still about who will become his
main challenger."
For more on the 2016 presidential race, see the Reuters
blog, "Tales from the Trail" (http://blogs.reuters.com/talesfromthetrail/)