CHARLESTON, S.C./MANCHESTER, N.H. (Reuters) - Flaring 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 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).